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DescriptionLM317isaadjustable3-terminalpositive-voltageregulator,thisbolgcoversLM317regulatoralternative,datasheet,applications,featuresandotherinformationonhowtouseandwheretousethisdevice.ABasicIntroductiontoLM317VoltageRegulatorCatalogDescriptionLM317PinoutLM317FeaturesLM317ApplicationsLM317CircuitLM317ParametersLM317CADModelLM317AdvantageLM317ElectricalCharacteristicsLM317PackageLM317AlternativesLM317EquivalentsWheretouseLM317HowtouseLM317LM317ManufacturerComponentDatasheetFAQOrdering&QuantityLM317PinoutPinNumberPinNameDescription1AdjustThispinsadjuststheoutputvoltage2OutputVoltage(Vout)Theregulatedoutputvoltagesetbytheadjustpincanbeobtainedfromthispin3InputVoltage(Vin)TheinputvoltagewhichhastoberegulatedisgiventothispinLM317FeaturesOutputvoltagerangeadjustablefrom1.25Vto37VOutputcurrentgreaterthan1.5AInternalshort-circuitcurrentlimitingThermaloverloadprotectionOutputsafe-areacompensationLM317ApplicationsATCAsolutionsDLP:3Dbiometrics,hyperspectralimaging,opticalnetworking,andspectroscopyDVRandDVSDesktopPCsDigitalsignageandstillcamerasECGelectrocardiogramsEVHEVchargers:levels1,2,and3ElectronicshelflabelsEnergyharvestingEthernetswitchesFemtobasestationsFingerprintandirisbiometricsHVAC:heating,ventilating,andairconditioningHigh-speeddataacquisitionandgenerationHydraulicvalvesIPphones:wiredandwirelessIntelligentoccupancysensingMotorcontrols:brushedDC,brushlessDC,lowvoltage,permanentmagnet,andsteppermotorsPoint-to-pointmicrowavebackhaulsPowerbanksolutionsPowerlinecommunicationmodemsPoweroverethernet(PoE)PowerqualitymetersPowersubstationcontrolsPrivatebranchexchanges(PBX)ProgrammablelogiccontrollersRFIDreadersRefrigeratorsSignalorwaveformgeneratorsSoftware-definedradios(SDR)Washingmachines:high-endandlow-endX-rays:baggagescanners,medical,anddentalLM317CircuitLM317ParametersOutputoptionsAdjustableOutputIout(Max)(A)1.5Vin(Max)(V)40Vin(Min)(V)3Vout(Max)(V)37Vout(Min)(V)1.25Noise(uVrms)38Iq(Typ)(mA)5ThermalresistanceJA(C/W)24Approx.price(US$)1ku|0.14Loadcapacitance(Min)(F)0RatingCatalogRegulatedoutputs(#)1FeaturesAccuracy(%)5PSRR@100KHz(dB)38Dropoutvoltage(Vdo)(Typ)(mV)2000Operatingtemperaturerange(C)0to125IhsManufacturerTEXASINSTRUMENTSINCBrandNameTexasInstrumentsLM317CADModelPackagePinsDownloadDDPAK/TO-263(KTT)3ViewoptionsSOT-223(DCY)4ViewoptionsTO-220(KCS)3ViewoptionsTO-220(KCT)3ViewoptionsLM317ElectricalCharacteristicsOverrecommendedrangesofoperatingvitualjunctiontemperature(unlessotherwisenoted)LM317PackageDDPAK/TO-263(KTT)SOT-223(DCY)TO-220(KCS)TO-220(KCT)LM317AlternativesSharethesamefunctionalityandpinoutbutisnotanequivalenttothecompareddevice:LM7805,LM7806,LM7809,LM7812,LM7905,LM7912,LM117V33,XC6206P332MR.LM317EquivalentsLT1086,LM1117(SMD),PB137,LM337(NegativeVariableVoltageregulator)WheretouseLM317WhenitcomestovariablevoltageregulationrequirementsLM317wouldmostlikelybethefirstchoice.Apartfromusingitasavariablevoltageregulator,itcanalsobeusedasafixedvoltageregulator,currentlimiter,Batterycharger,ACvoltageregulatorandevenasanadjustablecurrentregulator.OnenotabledrawbackofthisICisthatithasavoltagedropofabout2.5acrossitduringregulation,soifyoulookingtoavoidthatproblemlookintotheotherequivalentICsgivenabove.So,ifyouarelookingforavariablevoltageregulatortodelivercurrentupto1.5AthenthisregulatorICmightbetherightchoiceforyourapplication.HowtouseLM317LM317isa3-terminalregulatorICanditisverysimpletouse.Ithasmanyapplicationcircuitsinitsdatasheet,butthisICisknownforbeingusedasavariablevoltageregulator.So,letslookintohowtousethisICasavariablevoltageregulator.AssaidearliertheIChas3pins,inwhichtheinputvoltageissuppliedtopin3(VIN)thenusingapairofresistors(potentialdivider)wesetavoltageatpin1(Adjust)whichwilldecidetheoutputvoltageoftheICthatisgivenoutatpin2(VOUT).Nowtomakeitactasavariablevoltageregulatorwehavetosetvariablevoltagesatpin1whichcanbedonebyusingapotentiometerinthepotentialdivider.Thebelowcircuitisdesignedtotake12V(youcansupplyupto24V)asinputandregulateitfrom1.25Vto10V.TheResistorR1(1K)andthepotentiometer(10k)togethercreatesapotentialdifferenceatadjustpinwhichregulatestheoutputpinaccordingly.TheformulaetocalculatetheOutputvoltagebasedonthevalueofresistorsisVOUT=1.25(1+(R2/R1))Now,letsverifythisformulafortheabovecircuit.ThevalueofR1is1000ohmsandthevalueofR2(potentiometer)is5000becauseitisa10kpotentiometerplacedat50%(50/100of1000is5000).Vout=1.25(1+(5000/1000))=1.256=7.5VAndthesimulationshows7.7Vwhichisprettymuchclose.Youcanvarytheoutputvoltagebysimplyvaryingthepotentiometer.Inourcircuit,amotorisconnectedasaloadwhichconsumesaround650mAyoucanconnectanyloadupto1.5A.Thesameformulaecanalsobeusedtocalculatethevalueofresistorforyourequiredoutputvoltage.Oneeasywaytodothisistousethisonlinecalculatortorandomlysubstitutethevalueofresistorsyouhaveandcheckwhichoutputvoltageyouwillget.LM317ManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.ComponentDatasheetLM317DatasheetFAQWhatislm317usedfor?TheLM317servesawidevarietyofapplicationsincludinglocal,oncardregulation.Thisdevicecanalsobeusedtomakeaprogrammableoutputregulator,orbyconnectingafixedresistorbetweentheadjustmentandoutput,theLM317canbeusedasaprecisioncurrentregulator.Whatisthemaximuminputvoltageoflm317?TheLM317isanadjustablevoltagelinearregulatorthatcanoutput1.2537Vatupto1.5Acurrentwithaninputvoltagerangeof340V.Whatisthedifferencebetweenlm317andlm317t?Member.Thereisnofunctionaldifferenceastheyareoneinthesame.TheTattheendjustindicatesthatitsinaTO-220package.Theyusuallytagonextrathingsafterthepartnametoreferencethingslikepackage,temprange,etc.Islm317atransistor?TheLM317isanadjustablethree-terminalpositive-voltageregulatorcapableofsupplyingmorethan1.5Aoveranoutput-voltagerangeof1.25Vto32V....Byusingaheat-sinkedpasstransistorsuchasa2N3055(Q1)wecanproduceseveralampsofcurrentfarabovethe1.5ampsoftheLM317.Howdoesanlm317work?Thecircuitconsistsofalow-sideresistorandhigh-sideresistorconnectedinseriesformingaresistivevoltagedividerwhichisapassivelinearcircuitusedtoproduceanoutputvoltagewhichisafractionofitsinputvoltage.WhatisIClm317?TheLM317deviceisanadjustablethree-terminalpositive-voltageregulatorcapableofsupplyingmorethan1.5Aoveranoutput-voltagerangeof1.25Vto37V.Itrequiresonlytwoexternalresistorstosettheoutputvoltage.Thedevicefeaturesatypicallineregulationof0.01%andtypicalloadregulationof0.1%.HowdoIknowifmylm317isworking?Testinglm317t.Ifyoulooktotheic,thelegstowardsyou,therightoneistheinputpin.youmustseeadifferenceofminimum1.2Vbetweenthetwopins,otherwisetheICisfaulty.furthermore,thefirsttestistoseeifyouhaveinputvoltage!Whatistheworkingpricipleoflm317?LM317worksonaverysimpleprinciple.Itisavariablevoltageregulatori.e.supportsdifferentoutputvoltagelevelsforaconstantappliedinputvoltagesupply.HowtomakeasimplevoltageregulatorcircuitusingLM317?

DescriptionLM317isaadjustable3-terminalpositive-voltageregulator,thisbolgcoversLM317regulatoralternative,datasheet,applications,featuresandotherinformationonhowtouseandwheretousethisdevice.ABasicIntroductiontoLM317VoltageRegulatorCatalogDescriptionLM317PinoutLM317FeaturesLM317ApplicationsLM317CircuitLM317ParametersLM317CADModelLM317AdvantageLM317ElectricalCharacteristicsLM317PackageLM317AlternativesLM317EquivalentsWheretouseLM317HowtouseLM317LM317ManufacturerComponentDatasheetFAQOrdering&QuantityLM317PinoutPinNumberPinNameDescription1AdjustThispinsadjuststheoutputvoltage2OutputVoltage(Vout)Theregulatedoutputvoltagesetbytheadjustpincanbeobtainedfromthispin3InputVoltage(Vin)TheinputvoltagewhichhastoberegulatedisgiventothispinLM317FeaturesOutputvoltagerangeadjustablefrom1.25Vto37VOutputcurrentgreaterthan1.5AInternalshort-circuitcurrentlimitingThermaloverloadprotectionOutputsafe-areacompensationLM317ApplicationsATCAsolutionsDLP:3Dbiometrics,hyperspectralimaging,opticalnetworking,andspectroscopyDVRandDVSDesktopPCsDigitalsignageandstillcamerasECGelectrocardiogramsEVHEVchargers:levels1,2,and3ElectronicshelflabelsEnergyharvestingEthernetswitchesFemtobasestationsFingerprintandirisbiometricsHVAC:heating,ventilating,andairconditioningHigh-speeddataacquisitionandgenerationHydraulicvalvesIPphones:wiredandwirelessIntelligentoccupancysensingMotorcontrols:brushedDC,brushlessDC,lowvoltage,permanentmagnet,andsteppermotorsPoint-to-pointmicrowavebackhaulsPowerbanksolutionsPowerlinecommunicationmodemsPoweroverethernet(PoE)PowerqualitymetersPowersubstationcontrolsPrivatebranchexchanges(PBX)ProgrammablelogiccontrollersRFIDreadersRefrigeratorsSignalorwaveformgeneratorsSoftware-definedradios(SDR)Washingmachines:high-endandlow-endX-rays:baggagescanners,medical,anddentalLM317CircuitLM317ParametersOutputoptionsAdjustableOutputIout(Max)(A)1.5Vin(Max)(V)40Vin(Min)(V)3Vout(Max)(V)37Vout(Min)(V)1.25Noise(uVrms)38Iq(Typ)(mA)5ThermalresistanceJA(C/W)24Approx.price(US$)1ku|0.14Loadcapacitance(Min)(F)0RatingCatalogRegulatedoutputs(#)1FeaturesAccuracy(%)5PSRR@100KHz(dB)38Dropoutvoltage(Vdo)(Typ)(mV)2000Operatingtemperaturerange(C)0to125IhsManufacturerTEXASINSTRUMENTSINCBrandNameTexasInstrumentsLM317CADModelPackagePinsDownloadDDPAK/TO-263(KTT)3ViewoptionsSOT-223(DCY)4ViewoptionsTO-220(KCS)3ViewoptionsTO-220(KCT)3ViewoptionsLM317ElectricalCharacteristicsOverrecommendedrangesofoperatingvitualjunctiontemperature(unlessotherwisenoted)LM317PackageDDPAK/TO-263(KTT)SOT-223(DCY)TO-220(KCS)TO-220(KCT)LM317AlternativesSharethesamefunctionalityandpinoutbutisnotanequivalenttothecompareddevice:LM7805,LM7806,LM7809,LM7812,LM7905,LM7912,LM117V33,XC6206P332MR.LM317EquivalentsLT1086,LM1117(SMD),PB137,LM337(NegativeVariableVoltageregulator)WheretouseLM317WhenitcomestovariablevoltageregulationrequirementsLM317wouldmostlikelybethefirstchoice.Apartfromusingitasavariablevoltageregulator,itcanalsobeusedasafixedvoltageregulator,currentlimiter,Batterycharger,ACvoltageregulatorandevenasanadjustablecurrentregulator.OnenotabledrawbackofthisICisthatithasavoltagedropofabout2.5acrossitduringregulation,soifyoulookingtoavoidthatproblemlookintotheotherequivalentICsgivenabove.So,ifyouarelookingforavariablevoltageregulatortodelivercurrentupto1.5AthenthisregulatorICmightbetherightchoiceforyourapplication.HowtouseLM317LM317isa3-terminalregulatorICanditisverysimpletouse.Ithasmanyapplicationcircuitsinitsdatasheet,butthisICisknownforbeingusedasavariablevoltageregulator.So,letslookintohowtousethisICasavariablevoltageregulator.AssaidearliertheIChas3pins,inwhichtheinputvoltageissuppliedtopin3(VIN)thenusingapairofresistors(potentialdivider)wesetavoltageatpin1(Adjust)whichwilldecidetheoutputvoltageoftheICthatisgivenoutatpin2(VOUT).Nowtomakeitactasavariablevoltageregulatorwehavetosetvariablevoltagesatpin1whichcanbedonebyusingapotentiometerinthepotentialdivider.Thebelowcircuitisdesignedtotake12V(youcansupplyupto24V)asinputandregulateitfrom1.25Vto10V.TheResistorR1(1K)andthepotentiometer(10k)togethercreatesapotentialdifferenceatadjustpinwhichregulatestheoutputpinaccordingly.TheformulaetocalculatetheOutputvoltagebasedonthevalueofresistorsisVOUT=1.25(1+(R2/R1))Now,letsverifythisformulafortheabovecircuit.ThevalueofR1is1000ohmsandthevalueofR2(potentiometer)is5000becauseitisa10kpotentiometerplacedat50%(50/100of1000is5000).Vout=1.25(1+(5000/1000))=1.256=7.5VAndthesimulationshows7.7Vwhichisprettymuchclose.Youcanvarytheoutputvoltagebysimplyvaryingthepotentiometer.Inourcircuit,amotorisconnectedasaloadwhichconsumesaround650mAyoucanconnectanyloadupto1.5A.Thesameformulaecanalsobeusedtocalculatethevalueofresistorforyourequiredoutputvoltage.Oneeasywaytodothisistousethisonlinecalculatortorandomlysubstitutethevalueofresistorsyouhaveandcheckwhichoutputvoltageyouwillget.LM317ManufacturerTexasInstrumentsInc.(TI)isanAmericantechnologycompanythatdesignsandmanufacturessemiconductorsandvariousintegratedcircuits,whichitsellstoelectronicsdesignersandmanufacturersglobally.ItsheadquartersareinDallas,Texas,UnitedStates.TIisoneofthetoptensemiconductorcompaniesworldwide,basedonsalesvolume.TexasInstrumentssfocusisondevelopinganalogchipsandembeddedprocessors,whichaccountsformorethan80%oftheirrevenue.TIalsoproducesTIdigitallightprocessing(DLP)technologyandeducationtechnologyproductsincludingcalculators,microcontrollersandmulti-coreprocessors.Todate,TIhasmorethan43,000patentsworldwide.ComponentDatasheetLM317DatasheetFAQWhatislm317usedfor?TheLM317servesawidevarietyofapplicationsincludinglocal,oncardregulation.Thisdevicecanalsobeusedtomakeaprogrammableoutputregulator,orbyconnectingafixedresistorbetweentheadjustmentandoutput,theLM317canbeusedasaprecisioncurrentregulator.Whatisthemaximuminputvoltageoflm317?TheLM317isanadjustablevoltagelinearregulatorthatcanoutput1.2537Vatupto1.5Acurrentwithaninputvoltagerangeof340V.Whatisthedifferencebetweenlm317andlm317t?Member.Thereisnofunctionaldifferenceastheyareoneinthesame.TheTattheendjustindicatesthatitsinaTO-220package.Theyusuallytagonextrathingsafterthepartnametoreferencethingslikepackage,temprange,etc.Islm317atransistor?TheLM317isanadjustablethree-terminalpositive-voltageregulatorcapableofsupplyingmorethan1.5Aoveranoutput-voltagerangeof1.25Vto32V....Byusingaheat-sinkedpasstransistorsuchasa2N3055(Q1)wecanproduceseveralampsofcurrentfarabovethe1.5ampsoftheLM317.Howdoesanlm317work?Thecircuitconsistsofalow-sideresistorandhigh-sideresistorconnectedinseriesformingaresistivevoltagedividerwhichisapassivelinearcircuitusedtoproduceanoutputvoltagewhichisafractionofitsinputvoltage.WhatisIClm317?TheLM317deviceisanadjustablethree-terminalpositive-voltageregulatorcapableofsupplyingmorethan1.5Aoveranoutput-voltagerangeof1.25Vto37V.Itrequiresonlytwoexternalresistorstosettheoutputvoltage.Thedevicefeaturesatypicallineregulationof0.01%andtypicalloadregulationof0.1%.HowdoIknowifmylm317isworking?Testinglm317t.Ifyoulooktotheic,thelegstowardsyou,therightoneistheinputpin.youmustseeadifferenceofminimum1.2Vbetweenthetwopins,otherwisetheICisfaulty.furthermore,thefirsttestistoseeifyouhaveinputvoltage!Whatistheworkingpricipleoflm317?LM317worksonaverysimpleprinciple.Itisavariablevoltageregulatori.e.supportsdifferentoutputvoltagelevelsforaconstantappliedinputvoltagesupply.HowtomakeasimplevoltageregulatorcircuitusingLM317?

TheLM2940isacommonlow-dropout(LDO)linearregulator.ThisisacomprehensiveintroductiontoLM2940voltageregulator,fromitspinout,feature,parametertoitsapplication,itsdifferencebetweenLM7805andmore.CatalogLM2940DescriptionLM2940PinoutLM2940FeaturesLM2940ParametersLM2940EquivalentLM2940VSLM7805LM2940TypicalApplicationLM2940PackageLM2940ApplicationComponentDatasheetLM2940DescriptionTheLM2940isacommonlow-dropout(LDO)linearregulator.Thedropoutvoltageofaregulatoristhevoltagerequiredbetweentheinputandtheregulatedoutputvoltage.Theregulatorwastesthisvoltage(multipliedbycurrent),sothelowerthedropoutonalinearregulator,themoreefficientitis.ThismeansthattheLM2940,witha5Vdropoutat1amp,canbeusedwitha6voltwallwarttoprovidearegulated5Voutput.Thisalsomeansthattheregulatorwilloperateatamuchlowertemperaturethanastandard7805,whichwouldrequireamuchhigherinputvoltage(around7.5volts)foraregulated5Voutput.LM2940PinoutLM2940voltageregulatorLM2940PinoutPinNo.PinNameDescription1VinA(+ve)voltageisgivenasinputtothispin.2GNDCommontobothInputandOutput.3VoutOutputregulated12VistakenatthispinoftheIC.LM2940FeaturesInputVoltageRange=6Vto26VDropoutVoltageTypically0.5VatIOUT=1AOutputCurrentinExcessof1AOutputVoltageTrimmedBeforeAssemblyReverseBatteryProtectionInternalShortCircuitCurrentLimitMirrorImageInsertionProtectionP+ProductEnhancementTestedLM2940ParametersOutputoptionsFixedOutputIout(Max)(A)1Vin(Max)(V)26Vin(Min)(V)6Vout(Max)(V)15Vout(Min)(V)5Fixedoutputoptions(V)5,8,9,10,12,15Noise(uVrms)150Iq(Typ)(mA)10ThermalresistanceJA(C/W)23Loadcapacitance(Min)(F)22RatingCatalogRegulatedoutputs(#)1Features-Accuracy(%)2PSRR@100KHz(dB)48Dropoutvoltage(Vdo)(Typ)(mV)500Operatingtemperaturerange(C)-40to125,-40to85LM2940EquivalentTheequivalentforLM2940isLM7805.LM2940VSLM7805TheLM7805isapopularlinearvoltageregulatorbecauseitrequiresnoadditionalcomponentstooperate.Itisaverylow-costcomponent.Becauseofitscharacteristics,itreducestheoutputvoltageattheexpenseofheatdissipation,makingitinefficient.TheLM7805requiresaminimuminputvoltageof7.3Vtofunctionproperly.Itcanhandleamaximumcurrentof1A.Somemodelscanhandleupto1.5A.Itisrecommended,andinsomecasesrequired,tousecapacitorstoreduceoreliminatetheeffectsofthefrequenciesintroducedbytheotherelementsofthecircuit.Theyalsohelptoreducetheimpactofpeakconsumption.WhiletheLM2940isfromadifferentgeneration,butitspinisstillcompatiblewiththeLM7805.ItisaLow-dropout(LDO)LinearRegulatorthatismoreefficientthantheLM7805,butitwillrequirecapacitors.ThemaindifferencebetweenLM2940andLM7805isthatthemaximumoutputcurrentofLM2940is1A.ThemaximumoutputcurrentofLM7805is1.5A.Othersareveryclose,soifthecircuitonlyrequires1Aorbelow,LM2940canbeusedinsteadofLM7805.Whatsmore,the7805isexpendingtheexcesspowerasheat.Whichisverylossyespecialyifyourprojectusesbatteries.Theotherchipisabuckconverterissoitapproaches90%efficiencybyswitchingsothereisnowasteheat,thatswhyeventhoughLM7805ischeaperandeasiertousebuttheresstillalotofpeoplewouldgoforLM2940.LM2940LM7805SchematicComparisonLM2940SchematicLM7805SchematicLM2940TypicalApplicationLM2940PackageLM2940ApplicationPostregulatorforswitchingsuppliesLogicpowerSuppliesIndustrialInstrumentationComponentDatasheetLM2940DatasheetS8050isalow-powerNPNsilicontubewithamaximumcollector-base(Vcbo)voltageof40Vandacollectorcurrent(Ic)of0.5A.S8050isoneofthemostcommonlyusedsemiconductortransistormodelsincircuithardwaredesign.Name:S8050Type:NPNDissipatedpower:0.625W(SMD:0.3W)Collectorcurrent:0.5ABasevoltage:40VCatalogS8050PinoutS8050CircuitS8050ApplicationS8050FeaturesS8050AdvantageS8050AlternativesS8050EquivalentsWhereHowtouseS8050HowtoSafelyLongRunS8050inCircuitS8050PinoutPinNumberPinNameSymbolDescription1EmitterECurrentDrainsoutthroughemitter2BaseBControlsthebiasingoftransistor3CollectorCCurrentflowsinthroughcollectorS8050ApplicationAudioamplificationcircuitsClassBamplifiersPushpulltransistorsCircuitswherehighgainisrequiredLowsignalapplicationsS8050FeaturesLowVoltage,HighCurrentNPNTransistorSmallSignalTransistorMaximumPower:2WattsMaximumDCCurrentGain(hFE)is400ContinuousCollectorcurrent(IC)is700mABase-EmitterVoltage(VBE)is5VCollector-EmitterVoltage(VCE)is20VCollector-BaseVoltage(VCB)is30VHighUsedinpush-pullconfigurationdoeClassBamplifiersAvailableinTo-92PackageNote:CompleteTechnicalDetailscanbefoundattheS8050datasheetgivenattheendofthispage.S8050AdvantageS8050npntransistorS8050isaNPNtransistorhencethecollectorandemitterwillbeleftopen(Reversebiased)whenthebasepinisheldatgroundandwillbeclosed(Forwardbiased)whenasignalisprovidedtobasepin.Ithasamaximumgainvalueof400;thisvaluedeterminestheamplificationcapacityofthetransistornormallyS8050.Sinceitisveryhighitisnormallyusedforamplificationpurposes.However,atanormaloperatingcollectorcurrentthetypicalvalueofgainwillbe110.ThemaximumamountofcurrentthatcouldflowthroughtheCollectorpinis700mA,hencewecannotdriveloadsthatconsumemorethan700mAusingthistransistor.Tobiasatransistorwehavetosupplycurrenttobasepin,thiscurrent(IB)shouldbelimitedto5mA.Whenthistransistorisfullybiasedthenitcanallowamaximumof700mAtoflowacrossthecollectorandemitter.ThisstageiscalledSaturationRegionandthetypicalvoltageallowedacrosstheCollector-Emitter(VCE)orCollector-Base(VCB)couldbe20Vand30Vrespectively.Whenbasecurrentisremovedthetransistorbecomesfullyoff,thisstageiscalledastheCut-offRegion.S8050Alternatives2N3904,2N3906,2N2369,2N3055,S9014,MPSA42,SS8050,BC547S8050Equivalents2N5830,S9013S8050CircuitThisisavideointroducingtransistorsstereoamplifierS8050andS8550.WhereHowtouseS8050S8050transistorisageneral-purposetransistor,itisaperfecttransistortoperformsmallandgeneraltasksinelectroniccircuits.Youcanuseitasaswitchinelectroniccircuitstoswitchonloadsunder700mA.700mAisenoughtohandlevarietyofloadsforexamplerelays,LEDs,bulbsetc.Itcanalsobeusedasamplifierinsmallamplificationstagesorasaseparatesmallsignalamplifier.HowtoSafelyLongRunS8050inCircuitTosafelyrunS8050transistorinyourcircuitorelectronicprojectsdonotoperatethistransistorfromvoltagehigherthan20Vanddonotoperateanyloadmorethan700mAor0.7A.Useasuitablebaseresistorwhichwilllimitsthebasecurrenttoitsrequiredlevel.Donotexposeittoheatover150centigradeandbelow-60Centigrade.

MC33074

LM3914isamonolithicicthatsensesanalogvoltagelevelsanddrives10LEDs,providingalinearanalogdisplay.Asinglepinchangesthedisplayfromamovingdottoabargraph.ThisisanoverviewofLM3914dot/bardisplaydriver,wewillprovidetheinformationofitspinout,datasheet,parameter,andwherehowtousethisdeviceandsomuchmore.Top5electronicsProjectsusingLM3914-15IC|lm3914lm3915circuitsCatalogLM3914DescriptionLM3914PinoutLM3914FeaturesLM3914ParameterLM3914EquivalentWheretouseLM3914ICHowtouseLM3914ICLM3914CircuitLM3914PackageLM3914ApplicationComponentDatasheetLM3914DescriptionTheLM3914isamonolithicintegratedcircuitthatsensesanalogvoltagelevelsanddrives10LEDs,providingalinearanalogdisplay.Asinglepinchangesthedisplayfromamovingdottoabargraph.CurrentdrivetotheLEDsisregulatedandprogrammable,eliminatingtheneedforresistors.Thisfeatureisonethatallowsoperationofthewholesystemfromlessthan3V.TheLM3914isveryeasytoapplyasananalogmetercircuit.A1.2Vfull-scalemeterrequiresonly1resistorandasingle3Vto15Vsupplyinadditiontothe10displayLEDs.Ifthe1resistorisapot,itbecomestheLEDbrightnesscontrol.Thesimplifiedblockdiagramillustratesthisextremelysimpleexternalcircuitry.Wheninthedotmode,thereisasmallamountofoverlaporfade(about1mV)betweensegments.ThisassuresthatatnotimewillallLEDsbeOFF,andthusanyambiguousdisplayisavoided.Variousnoveldisplaysarepossible.TheLM3914isratedforoperationfrom0Cto+70C.TheLM3914N-1isavailableinan18-leadPDIP(NFK)package.LM3914PinoutLM3914LM3914PinoutPinNumberPinNameDescription1and10to18LED1,LED2,LED3.....LED10The10LEDswhichhastobecontrolledisconnectedtothesepins2V-/GroundGroundpinoftheIC3V+/VccSupplyVoltage(3-18)V4RLOLowlevelvoltageforpotentialdivider5SignalAnalogsignalInputpinbasedonwhichtheLEDiscontrolled.6RHIHighLevelvoltageforpotentialdivider7REFOUTOutputReferenceVoltageforLEDcurrentlimiting8REFADJAdjustpinforvoltagereference9ModeSelectbetweenDot/BarModeLM3914FeaturesAnalogControlledLEDDriverICNumberofcontrollableLEDs:10OperatingVoltage:3Vto18VInputAnalogvoltagerange:1.2Vto12VLEDsinkcurrent:2mAto30mA(programmable)BothDot/BarmodeavailableCanbecascadedtocontrolupto100LEDsAvailablein18-pinDIP,PLCCpackageItcandriveLCDs,LEDsotherwisevacuumfluorescents.Thedototherwisebotdisplaymodecanbeselectedbytheuserexternally.Itcanbeexpandableupto100displays.LM3914ParameterManufacturer:TexasInstrumentsSeries:-Packaging:TubePartStatus:ObsoleteDisplayType:LEDLCDVacuumFluorescent(VF)Configuration:Dot/BarDisplayInterface:-DigitsorCharacters:10StepsCurrent-Supply:6.1mAVoltage-Supply:3V~20VOperatingTemperature:0C~70CMountingType:ThroughHolePackage/Case:18-DIP(0.3007.62mm)SupplierDevicePackage:18-PDIPBasePartNumber:LM3914LM3914EquivalentLM3914EquivalentLEDDriver:LM3916AlternativeLEDDriverICs:CD4511,MAX7219,CD4054WheretouseLM3914ICTheLM3914isananalogcontrolledLEDdriverIC,whichmeansthatitcancontrol(turnonoroff)10LEDlightsusingananaloginputvoltage.Thisintegratedcircuiteliminatestheneedforamicrocontrollerandprogramming,aswellasthehardwarerequiredtocontroltenLEDs.Theanaloginputvoltagecanrangefrom3Vto18V,andtheLEDcurrentcanbecontrolledwithasingleresistoronpin7.(RefOut).TheICalsohastwooperatingmodes:DOTmodeandBARmode,andupto100LEDscanbecontrolledbycascadingmultipleICs.TheseICsarecommonlyusedinvisualalarmsandothermetering/monitoringapplicationsbecausetheLEDscanbecontrolledwithoutflickeringandflawlesslywithequalbrightness.So,ifyourelookingforanICtopoweryourbarLEDlightsoranother10-LEDsequence,thisICmightbeofinteresttoyou.HowtouseLM3914ICThebenefitofusingLM3914isthatitrequireslittlehardwareandissimpletosetup.Simplyconnectthe10LEDstotheIC,setthereferencevoltagesfortheinputvoltage,andlimitthecurrentthroughtheLED,andweredone.ThecircuitbelowisanexampleofanLM3914applicationcircuit.SimplyconnecttheV+andV-topowertheIC,andtheanalogsignalvoltageisconnectedtopin5.Inthiscase,weused9VtopowertheICandmonitorananalogyvoltagerangingfrom0to5V.AlwayskeepinmindthatthevoltageusedtopowertheIC(inthiscase,9V)shouldbeatleast1.5Vhigherthanthemonitoringvoltage(here5V).Becausewearemonitoring0-5Vhere,wesetthelowreferencevoltage(pin4)to0Vandthehighreferencevoltage(pin6)to5V.Asyoumayhavenoticed,weconnectedalltenLEDsdirectlytotheICwithoutusinganycurrentlimitingresistors.ThisisbecausetheIChasaninternalcurrentlimiterandthecurrentvaluecanbesetusingthepinVRO(pin7).Thecurrentcalculationformulasaregivenbelow,whereIisthecurrentflowingthrougheachLEDandRListheresistorconnectedtopin7.I=12.5/RLIntheprecedingexample,weuseda470ohmresistorasRl,sothecurrentthrougheachLEDwillbearound25mA;youcanchangethevalueasneeded.Also,thecathodeoftheLEDisconnectedtotheIC,whiletheanodeisconnectedto+5V.ThisisduetothefactthattheICoutputpinscanonlysinkcurrentandnotsourceit.Theintegratedcircuit(IC)canoperateintwomodes:dotmodeandbarmode.Indotmode,themodepin(pin9)mustbeleftfloating;inthismode,basedontheinputvoltage,onlyoneLEDwillbeturnedon.InBarmode,connectthemodepin(pin9)toV+,andtheLEDwillturnonandoffsequentiallybasedontheinputvoltage.Boththemodesareshowninthegiffileabove.LM3914CircuitThecircuitdiagramforICLM3914isshownbelow.Thecircuitcanbeconstructedusingbothbasicelectricalandelectroniccomponents.TheICLM3914isacriticalcomponentofthiscircuit.AnalarmdrivingswitchforoverrangecanbeconnectedtoabartypeLMseriesLEDdrivingdisplaycircuitinthefollowingcircuit.Thiscircuitissuitableforbardisplays.LM3914BasedAlarmDriverCircuitThecircuithereemploysaPNPtransistor,denotedbyQ1.ThistransistorcanbeconnectedbetweentheLEDpositiveandnegativeterminals,andthebaseterminalofthetransistorisconnectedtotheICspin-10todrivetheLED10.Inseries,analarmunitisconnectedtothetransistorscollectorterminal.Normally,Q1transistor,LED10,andthealarmunitareallturnedoff;however,ifLED10isactivated,itpullsQ1transistorthroughresistorR2andthusactivatesthealarmunit,indicatingthattheconditionisoutofrange.Intheabovecircuit,analarmunitgeneratesanacousticalarmsoundusingapiezosirenunit,otherwiseagatedastableswitchunitthatcontinuouslyactivatestheLEDbrightnessbetweenhighandlowlevelsbeneaththeover-rangestate,oracombinationofboth.Ifdesired,theunitcanbeswitchedtoanyoftheLEDdisplays,andthealarmwillsoundifthatoranyotherhighLEDisenergized.LM3914PackageLM3914ApplicationBatteryMeterforRobotMonitoringof12VCarBatteryTesterCircuitforSoilMoistureMonitoringofLeadAcidBatteryChargerChargeMonitoringCircuitforAtmosphericKitchenExhaustFanforControllingTemperatureMeterCircuitforTemperatureDigitalgaugesElectronicdisplaysLow-costmonitordevicesCrudeBatterylevelindicatorsFadebarsComponentDatasheetLM3914DatasheetIDescriptionThisblogusestheuniversalintegratedchipTL494toconvertanalogsignalsintoPWM(pulsewidthmodulation)signals.Intheoutputpart,N-channelMOSFETandP-channelMOSFETareusedtoformaswitchingpoweramplifier.CatalogIDescriptionIIIntroduction2.1SwitchingPowerAmplifierOverview2.2TL494IntroductionIIISchemeDesign3.1DutyCycleAdjustmentCircuit3.2InputSignalCompressionCircuit3.3MOSFETDriveCircuit3.4WorkingPrincipleofOutputPartIVExperimentalResultsVConclusionFAQOrdering&QuantityIIIntroduction2.1SwitchingPowerAmplifierOverviewWiththerapiddevelopmentofhigh-speedpowerMOSFETproductiontechnology,theoperatingfrequencyofMOSFETisgettinghigherandhigher,thedrivingmethodisgettingsaferandthepriceisgettinglower.Therefore,alargenumberofswitchingpoweramplifiersappliedtovarioushouseholdappliancesandindustrialalarmshaveappearedonthemarketinrecentyears.Comparedwiththelinearpoweramplifier,althoughthecircuitoftheswitchingpoweramplifierisslightlymorecomplicated.Butitisveryefficientandcanreducethesizeoftheheatsink,evenwithoutusingtheheatsink.Therefore,thevolumeoftheproductcanbegreatlyreduced.2.2TL494IntroductionTL494isaswitchingpowersupplypulsewidthmodulation(PWM)controlchip.Formanyyears,asthecheapestdouble-endedPWMchip,TL494hasbeenwidelyusedindouble-endedtopologiessuchaspush-pullandhalf-bridge.Becauseofitsloweroperatingfrequencyandsingle-endedoutputportcharacteristics.Itisoftenusedwithpowerbipolartransistors(BJT).IfusedwithpowerMOSFET,anexternalcircuitisrequired.TL494worksinawidevoltagerangefrom7Vto40V,withamaximumoperatingfrequencyof200kHz,withtheinternalsawtoothgenerator,PWMgenerator,andlagtimeadjustmentfunctions.IIISchemeDesignFigure1isablockdiagramofaTL494-basedswitchingpoweramplifier.Thekeytothecircuitdesignisthedutycycleadjustmentcircuit,inputsignalcompressioncircuit,andMOSFETdrivecircuit.Figure1.TL494SwitchingPowerAmplifier3.1DutyCycleAdjustmentCircuitThedutycycleisthekeytoimprovingvoltageutilizationduringPWMsignalmodulation.BecauseTL494isanintegratedchipforswitchingpowersupply.Therefore,theminimumlagtimeissetto0.1Vinternally.Themaximumdutycycleisapproximately96%attheoutputofthetransmitterstage.Figure2showstheinputpartandpartofthecircuitforPWMsignalmodulation.Figure2.SignalInputsectionandPWMGeneratorInFigure2,whenC4=1000pFandR4=24k,theoperatingfrequencyisabout78kHz.IfthereisnodutycycleadjustmentcircuitD8,D17,R23,becausethecomparisonpointoftheinternaldelaytimecomparatoris0.1V.Sotheminimumon-timeisabout1.52s,andtheminimumdutycycleisD=1.52/1312%.Therefore,thevoltageutilizationratewilldecreaseduringPWM.IfD8,D17,andR23areused,a0.82VbiasvoltagewillbegeneratedatthepointEofthecapacitorC4forthesawtoothwavegeneration,andthestartingpointofthesawtoothwavewillbeincreasedfrom0Vto0.82V.Therefore,theon-timeisreducedto0.64s,andtheminimumdutycycleisreducedtoD=0.64/134.9%.Thiscansignificantlyimprovethevoltageutilization.Figure3istheoutputwaveformwhenthereisnodutycycleadjustmentcircuit.Figure4istheoutputwaveformwhenthereisadutycycleadjustmentcircuit.Figure3.OutputWaveformwithoutDutyCycleAdjustmentCircuitFigure4.OutputWaveformwithDutyCycleAdjustmentCircuit3.2InputSignalCompressionCircuitBecausetheinputsignalofthealarmhasalargevariationrange,itisnecessarytocompressthesignalwithalargeamplitudeaccordingtoacertainratio.InFigure2,R6,R16,D10,D11constitutetheinputsignalcompressioncircuit,anditskeyistousetheinputcharacteristicsofthediode.Figure5showsitsinputcharacteristics.Amongthem,D10andD11areconnectedinparalleltocompresssignalsinbothpositiveandnegativedirections.Figure5.OutputCharacteristicsofInputSignalCompressionCircuitThecompressionratiodependsonthevaluesofR6andR16.Thelargerthevalue,thelargerthecompressionratio.ByadjustingthevaluesofR6andR16,thechangerangeofthecompressedsignalissetto-0.82V~0.82V.Theamountofchangeis1.64V.WecanseeFigure4,thesawtoothvoltagevariationrangeis0.82V~3.25V.SotheoutputsignalvariationrangeoftheTL494internalerroramplifieris2.43V.ThegainoftheinternalerroramplifierdependsonR7andR20.Byadjustingtheirvalues,whentheamountofchangeofthecompressedsignalis1.64V,theoutputsignalchangerangeoftheinternalerroramplifiercanbesetto2.43V.Sincemostalarmsusetweeters,thebasswithalargeamplitudecanbegreatlyreduced.3.3MOSFETDriveCircuitP-channelMOSFETusesIRF9540.Ithasthecharacteristicsofthemaximumoperatingvoltageof100V,themaximumoperatingcurrentof18A,andsaturationwhenVGSvoltageis5V~15V.N-channelMOSFETusesIRF540.Ithasthecharacteristicsofthemaximumoperatingvoltageof100V,themaximumoperatingcurrentof27A,andsaturationwhenVGSvoltageis5V~15V.ThedrivingtransistorQ3adoptsNPNtypeC8050,andQ7adoptsPNPtypeC8550.Bothofthesetwodrivetransistorshavethecharacteristicsofamaximumoperatingvoltageof30V,amaximumoperatingcurrentof1A,andaVBEof12V.Figure6showstheMOSFETdrivecircuit.Figure6.MOSFETDriveCircuitFigure7showstheMOSFETdrivingprinciplewaveform.WhenthepulsevoltageatpointAislow,thecurrentflowsthroughthereversebiasoftheZenerdiodeD7andthetransistorQ3toformaVGSvoltage,andQHisturnedon.WhenthepulsevoltageatpointAishigh,thecurrentflowsthroughthereversebiasoftheZenerdiodeD9andthetransistorQ7toformaVGSvoltage,andQListurnedon.Inaddition,Figure7alsoshowsdetaileddrivingwaveforms.lWhenthepulsevoltageislow,thevoltageislowerthanVLtomakeQHturnon.lWhenthepulsevoltageishigh,itsvoltageishigherthanVHtomakeQLturnon.IttakesacertainamountoftimetochangefromVLtoVH.Atthistime,QHandQLwillbecutoffatthesametime.Therefore,thepulsechangeprocessisverysafe.Figure7.MOSFETDrivingPrincipleWaveformTheVGSofQHandQLisdeterminedbythefollowingformula:Where:VGSisthedrivingvoltageofMOSFET;VCisthepowersupplyvoltage;VDistheregulatedvoltageofZenertubesD7andD9(usuallythesameZenertubeisused);VBEisthecounterbreakdownvoltageofC8050andC8550.Figure8isthemeasureddrivewaveform.Whenthepulsevoltagechangesfromlowtohigh,thetimeforQHandQLtocutoffatthesametimeisabout100~300ns.Figure8.MeasuredDriveWaveform3.4WorkingPrincipleofOutputPartAsshowninFigure6,theoutputpartconsistsofQH,QLandL3,C8,C5,andC7.TheoutputvoltageistransmittedtotheloadafterfilteringhighfrequencywavesthroughL3andC8.Generally,anelectrolyticcapacitorisusedattheoutputend,butthiscircuitusesC5andC7toformahalfbridge,andthenconnectthemidpointtotheload.Theadvantageofthisconnectionmethodisthatthetwocapacitorsarenotonlythetransmissionpathoftheoutputsignal(thecapacitancevalueistheparallelvalueofthetwocapacitors),butalsohasafilteringeffectonthepowersupply(thecapacitancevalueistheseriesvalueofthetwocapacitorsatthistime),andreducetheinternalpressureofthecapacitorbyhalf.IVExperimentalResultsTable1showsthequiescentcurrentwhentheinputvoltageis35Vandtheoperatingfrequencyis78kHzwhenusingdifferentvoltageregulatordiodes.ItcanbeseenfromTable1:Whenthevoltageregulationvalueofthevoltagestabilizingdiodeis0V,5V,thedistancebetweentheconductionpointsofVLandVHistooclose,andtheconductiontimeistoolong,andthereisalargerstaticcurrent.Althoughthecurrentisrelativelysmallat20V,theMOSFETgeneratessevereheat.AscanbeseenfromTable1,whentheoperatingvoltageis35V,theselectionrangeoftheZenerdiodeis7.5V~15V.VConclusionTheexperimentalresultsshowthatthePWMsignalofTL494isusedforN-channelMOSFETandP-channelMOSFETtoformaswitchingpoweramplifierwithauniquedrivingmodetoovercometheshortcomingsofsimultaneousconductionoftwopowerMOSFETs.Notonlythat,italsohasidealdrivewaveforms,efficiencygreaterthan95%,goodbandwidthandlowprice,whichfullymeetstherequirementsofindustrialalarms.Andunder18Woutputpower,comparedwiththepoweramplifiercomposedofTDA7481,thereisnotmuchdifference,andthereisbasicallynoheatingphenomenon,andtheheatsinkcanberemoved.Ifyouwanttogetmoreoutputpower,youonlyneedtoincreasetheworkingvoltagetomorethan35VandfitaproperZenerdiode.FAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?IDescriptionTL494,isaswitchingpowersupplypulse-widthmodulation(PWM)controlchip.DesignedandintroducedbyTexasInstrumentsintheearly1980s,theTL494gainedimmediateandwidespreadmarketacceptance,especiallyinATXhalf-bridgepowersuppliesforPCcomputers.TL494PWMControllerTL494hasbecomeanindustry-standardchip,producedbymanyintegratedcircuitmanufacturers.Widelyusedinsingle-endedforwarddual-tube,half-bridge,andfull-bridgeswitchingpowersupplies.TL494hastwopackagingforms,SO-16andPDIP-16,tomeettherequirementsofdifferentoccasions.CatalogIDescriptionIITL494FeaturesIIITL494InternalStructure3.15VReferenceSource3.2SawtoothOscillator3.3OperationalAmplifier3.4Comparator3.5PulseTrigger3.6QuietTimeComparatorIVTL494WorkingPrincipleVConclusionFAQOrdering&QuantityIITL494FeaturesCompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeInternalRegulatorProvidesaStable5-VReferenceSupplyWith5%ToleranceCircuitArchitectureAllowsEasySynchronizationIIITL494InternalStructureFigure1.TL494InternalStructure3.15VReferenceSourceTL494hasabuilt-inreferencesourcebasedonthebandgapprinciple.Thestableoutputvoltageofthereferencesourceis5V.TheconditionisthattheVCCvoltageisabove7V.Theerroriswithin100mV.Theoutputpinofthereferencesourceisthe14thpinREF.3.2SawtoothOscillatorTL494hasabuilt-inlinearsawtoothwaveoscillator,whichgeneratesa0.3~3Vsawtoothwave.TheoscillationfrequencycanbeadjustedbyanexternalresistorRtandacapacitorCt.Itsoscillationfrequencyis:f=1/Rt*CtAmongthem:TheunitofRtisohm;TheunitofCtisfarad.ThesawtoothwavecanbemeasuredattheCtpin.3.3OperationalAmplifierTL494integratestwooperationalamplifierspoweredbyasinglepowersupply.Thetransferfunctionoftheoperationalamplifierisft(ni,inv)=A(ni-inv),butitcannotexceedtheoutputswing.Ingeneralpowercircuits,theop-ampisconnectedtooperateinaclosed-loop.Open-loopisusedinafewspecialcases,andthesignalisinputfromtheoutside.Theoutputterminalsofthetwooperationalamplifiersarerespectivelyconnectedtoadiode,whichisconnectedtotheCOMPpinandthesubsequentcircuit(comparator).Thisensuresthatthehigheroutputofthetwoop-ampsentersthesubsequentcircuit.3.4ComparatorThesignal(COMPpin)outputbytheoperationalamplifierentersthepositiveinputterminalofthecomparatorinsidethechipandiscomparedwiththesawtoothwaveenteringthenegativeinputterminal.WhenthesawtoothwaveishigherthanthesignaloftheCOMPpin,thecomparatoroutputs0,otherwise,itoutputs1.3.5PulseTriggerThepulseflip-flopturnsonatthefallingedgeofthesawtoothwaveandthecomparatoroutputs1.Thismakesoneofthetwooutputs(inturn)on-chiptransistorsareturnedonandcutoffwhenthecomparatoroutputdropstozero.3.6QuietTimeComparatorThedeadzonetimeissetbyDeadTimeControlpin4.Itusesacomparatortointerferewiththepulsetriggerandlimitthemaximumdutycycle.Theupperlimitofthedutycycleofeachendcanbesetupto45%,andtheupperlimitofthedutycycleisabout42%whentheoperatingfrequencyishigherthan150KHz.(WhentheDTCpinlevelissetto0).IVTL494WorkingPrincipleTL494isafixedfrequencypulsewidthmodulationcircuitwithabuilt-inlinearsawtoothoscillator.Theoscillationfrequencycanbeadjustedbyanexternalresistorandacapacitor.Theoscillationfrequencyisasfollows:ThewidthoftheoutputpulseisachievedbycomparingthepositivesawtoothvoltageonthecapacitorCTwiththeothertwocontrolsignals.ThepoweroutputtubesQ1andQ2arecontrolledbyaNORgate.Itwillbestrobedwhentheclocksignaloftheflip-flopislow.Thatis,itwillbegatedonlywhenthesawtoothvoltageisgreaterthanthecontrolsignal.Whenthecontrolsignalincreases,theoutputpulsewidthwilldecrease.Wecantakealookatthepicturebelow.Figure2.TL494PulseControlWaveform​Thecontrolsignalisinputfromtheoutsideoftheintegratedcircuit.Oneissenttothedeadtimecomparator,andoneissenttotheinputoftheerroramplifier.Thedead-timecomparatorhasaninputcompensationvoltageof120mV,whichlimitstheminimumoutputdead-timetoapproximately4%ofthesawtoothperiod.Whentheoutputterminalisgrounded,themaximumoutputdutycycleis96%.Whentheoutputterminalisconnectedtothereferencelevel,thedutycycleis48%.Whenthedeadtimecontrolinputisconnectedtoafixedvoltage(rangebetween0-3.3V),additionaldeadtimecanbegeneratedontheoutputpulse.Thepulsewidthmodulationcomparatorprovidesameansfortheerroramplifiertoadjusttheoutputpulsewidth.Whenthefeedbackvoltagechangesfrom0.5Vto3.5,theoutputpulsewidthdropstozerofromthemaximumon-percentagetimedeterminedbythedeadzone.Thetwoerroramplifiershaveacommonmodeinputrangefrom-0.3Vto(Vcc-2.0),whichmaybedetectedfromtheoutputvoltageandcurrentofthepowersupply.Theoutputoftheerroramplifierisalwaysatahighlevel.ItperformsORoperationwiththeinvertinginputterminalofthepulsewidthmodulator.Itisthiscircuitstructurethattheamplifiercandominatethecontrolloopwithminimaloutput.WhenthecomparatorCTdischarges,apositivepulseappearsattheoutputofthedeadzonecomparator,andtheflip-flopconstrainedbythepulseistimed.AtthesametimestoptheworkoftheoutputtubesQ1andQ2.Iftheoutputcontrolterminalisconnectedtothereferencevoltagesource,themodulatedpulseisalternatelyoutputtothetwooutputtransistors,andtheoutputfrequencyisequaltohalfofthepulseoscillator.Ifitworksinasingle-endedstateandthemaximumdutycycleislessthan50%,theoutputdrivesignalisobtainedfromthetransistorQ1orQ2respectively.Afeedbackwindinganddiodeoftheoutputtransformerprovidefeedbackvoltage.Insingle-endedoperatingmode,whenahigherdrivecurrentoutputisrequired,Q1andQ2canalsobeusedinparallel.Atthistime,theoutputmodecontrolpinneedstobegroundedtoturnofftheflip-flop.Inthisstate,theoutputpulsefrequencywillbeequaltotheoscillatorfrequency.VConclusionThisblogsummarizesthecharacteristics,internalstructureandworkingprincipleofTL494.AlthoughthearchitectureofTL494hasbeenproventobeextremelyexcellentinhistory,itisfacingeliminationinthehigh-endmarketduetoitsoldtechnology,lowfrequency,andlackofnewenergy-savingfeatures.However,itisworthmentioningthatTL494isstillwidelyadoptedinthelow-endandmid-endmarkets.FAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?

MC33074

IDescriptionThisblogintroducesapulsewidthmodulationtechnologywithTL494asthecontrolcore.AnditisappliedtoDCmotorcontrolsystem.Theworkingprincipleofthesystem,therealizationcircuitandthestructureandspecificapplicationofthePWMcontrolchipareanalyzedindetail.CatalogIDescriptionIIWorkingPrincipleandRealizationofControlSystem2.1HowSystemWorks2.2SelectionofPWMControlChip2.3RealizationCircuitofSystemIIISimulationResultsIVConclusionFAQOrdering&QuantityIIWorkingPrincipleandRealizationofControlSystem2.1HowSystemWorksThebasicdesignideaofthiscontrolsystemistouseastep-downchoppercircuitasshowninFigure1.Figure1.Step-downChopperCircuitanditsWaveformInthefigure,theDCpowersupplyisUd,andtheloadisamotor(M).Whentheswitchingdevice(VT)istriggeredandturnedon,theDCvoltageisappliedtothemotorforadurationoft1.Whenthefieldswitchingdeviceisturnedoff,thevoltageontheloadiszeroandlastsfort2time.IfwedefinethedutycycleT=t1+t2,andthedutycyclek=t/T,thewaveformdiagramandtheprincipleoftheDCchoppercircuitareasfollows:Theaveragevalue(Uo)ofthesystemoutputvoltageis:Theeffectivevalue(U)ofitsoutputvoltageis:Thepulsewidthmodulation(PWM)workingmodeadoptedbythissystemkeepsTunchangedandt1changes.TheprincipleblockdiagramofthecontrolsystemisshowninFigure2.Figure2.ControlSystemBlockDiagramThepowersupplyinthissystemmakesthemotorworkthroughthepowerdrivecircuit.Theon-offofthepowerdrivecircuitiscontrolledbythePWMcontrolchip.ThesystemsamplesthemotorcurrentfeedsitbacktothePWMcontrolchipandcomparesitwiththecurrentvalueofthecurrentcomparisoncircuit.TocontrolthePWMsignaloutputtoachievethepurposeofspeedregulation.ThesystemalsosamplesthepowersupplyvoltageandfeedsitbacktothePWMcontrolchip.Inthisway,itcanbecomparedwiththevoltagevalueofthevoltagecomparisoncircuittocontrolthePWMsignaloutputandachievetheeffectofUndervoltageprotection.WeusethecommonBUCKcircuitforthepowerdrivecircuitandPowerMOSFETfortheswitchtube.Theregulationofitsoutputvoltageisrealizedbycontrollingtheturn-ontimeofthedevice.Consideringtheinfluenceoftheinductanceofthemotor,theoutputcurrentisrelativelystableandtheenergyconsumptionislow.2.2SelectionofPWMControlChipInthecontrolcircuitofthemotorPWMcontrolsystem,theTL494chipisselected.TL494chiphasthefeaturesofstronganti-interferenceability,simplestructure,highreliabilityandlowprice.TheinternalcircuitofTL494(Figure3)consistsofthefollowingparts:Thereferencevoltagegeneratingcircuit;Oscillationcircuit;Intermittentadjustmentcircuit;Twoerroramplifiers;Pulsewidthmodulationcomparator;Outputcircuit;...Figure3.TL494InternalStructureAmongthem:Forpins1and2,theyarethenon-invertingandinvertinginputterminalsoferroramplifier1.Forpin3,itisphasecorrectionandgainscontrol.Forpin4,itisanintermittentperiodofconditioning,andthecut-offtimecanbechangedfrom2%to100%whenavoltageof0~3.3Visappliedtoit.Forpins5and6,theyareusedtoconnectexternaloscillationresistorRTandoscillationcapacitorCTtodeterminethefrequencyfoscofthesawtoothwavegeneratedbytheoscillator.Where:ThevaluerangeofRTandCT:RT=5~100kQ,CT=0.001~0.1F.Pin7isthegroundterminal;Forpins8,9and11,10,theyarethecollectorandemitterofthetwofinaloutputtransistorsinsideTL494;For12feet,itisthepowersupplyterminal;Forpin13,itistheoutputcontrolterminal.Whenthispinisgrounded,itisaparallelsingle-endedoutputmode.Whenpin14isconnected,itisapush-pulloutputmode;For14feet,itisthe5Vreferencevoltageoutputterminal,themaximumoutputcurrentis10mA;For15and16pins,theyaretheinvertingandnon-invertinginputterminalsoftheerroramplifier2.2.3RealizationCircuitofSystemTheconcreterealizationcircuitofthiscontrolsystemisshowninFig.4.Thesystemusescurrentnegativefeedbacktotrackthespeedofthemotor.Atthesametime,throughthenegativefeedbackofthevoltageofthepowersupply,thesystemhasthefunctionofundervoltageprotection.Figure4.SystemImplementationCircuitThemotorcurrentisdetectedandfedbacktopin1oftheerroramplifier1oftheTL494,comparedwiththecurrentreferencesignalofpin2tocontrolthePWMoutputofTL494.Soastorealizethefunctionofregulatingthespeedofthemotor.Byadjustingtheresistancevalueoftheadjustableresistor(RES1).Thatis,changethesizeofthesetcurrentreferencesignaltoadjustthedutycycleofthePWMoutputsignal.Soastoachievethepurposeofadjustingthemotorspeed.Bysamplingthevoltageofthepowersupply,itisfedbacktopin15oftheinternalerroramplifier2ofTI494.Thencomparewiththevoltagereferencesignalofpin16tocontrolthePWMoutputofTL494.Soastorealizetheundervoltageprotectionfunctionofthesystem.ThesystempowerisdrivenbyPowerMOSFET,whichhasahighinputimpedanceandcanbedirectlydrivenbyatransistor.Pin13ofTI494isusedtocontroltheoutputmode.Inthissystem,choosetoinputthisendaslowlevel.Atthistime,theflip-flopsQ1andQ2intheTL494donotwork,thetwooutputsarethesame,thefrequencyisthesameastheoscillatorfrequency,andthemaximumdutycycleis98%.IIISimulationResultsInordertoverifytheeffectivenessofthesystem,wecansimulatethecircuitoftheabove-mentionedDCmotorcontrolsystembasedonPWMtechnologybycomputer.WesetthesystemspowersupplyvoltageUcc=12V,DCmotorratedparameters:Un=12V,In=15A,4poles,armatureresistanceRa=0.21Q,momentofinertiaJ=0.57kg㎡.ThroughchangingtheadjustableresistanceRES1ofthecontrolcircuittorealizethedifferentdutyratioofthesystemoutput.Whentheoutputdutyratiois0.2,0.65/0.8,thevoltageandcurrentwaveformsofthemotorareshowninFigure5.Figure5.MotorVoltageandCurrentWaveformItcanbeseenfromFigure5thatwhenoutputtingdifferentdutyratios,thevoltageandcurrentwaveformsofthemotorarestable,whichisconducivetothelong-termstableoperationofthemotor.ThisshowsthattheTL494-basedPWMcontroltechnologyintroducedinthisarticleisfeasibleinpracticalapplicationsandrunsstably.IVConclusionThisblogsummarizesaPWMcontroltechnologybasedontheTL494chip.Thesimulationresultsshowthatthesystemhasasimplestructure,lowenergyconsumption,andstableoperation.AndthecharacteristicsoftheTL494chiphavebeenfullyutilizedsothatthesystemhastheadvantagesofundervoltageprotection.FAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?DescriptionTL494wasdesignedandlaunchedbyTexasInstrumentsintheearly1980s.Itwaswidelyacceptedbythemarketimmediatelyafteritwaslaunched,especiallyontheATXhalf-bridgepowersupplyofPCs.Untiltoday,aconsiderableproportionofPCpowersuppliesarestillbasedontheTL494chip.HowtoTestTL494NCatalogDescriptionComponentDatasheetTL494PinoutTL494ParameterFeaturesAdvantagesApplicationsTL494SimplifiedBlockDiagramTL494PackageandPinsFunctionalBlockDiagramWheretouseTL494HowtouseTL494TL494TypicalApplicationFAQOrdering&QuantityComponentDatasheetDatasheetTL494Pulse-Width-ModulationControlCircuitsdatasheet(Rev.H)Applicationnotes1IsolatedMultipleOutputFlybackConverterDesignUsingTL494Applicationnotes2DesigningSwitchingVoltageRegulatorsWiththeTL494(Rev.E)TL494PinoutPinDescriptionNameNO.1IN+1Noninvertinginputtoerroramplifier11IN2Invertinginputtoerroramplifier12IN+16Noninvertinginputtoerroramplifier22IN-15Invertinginputtoerroramplifier2C18CollectorterminalofBJToutput1C211CollectorterminalofBJToutput2CT5CapacitorterminalusedtosetoscillatorfrequencyDTC4Dead-timecontrolcomparatorinputE19EmitterterminalofBJToutput1E210EmitterterminalofBJToutput2FEEDBACK3InputpinforfeedbackGND7GroundOUTPUTCTRL13Selectssingle-ended/paralleloutputorpush-pulloperationREF145-VreferenceregulatoroutputRT6ResistorterminalusedtosetoscillatorfrequencyVCC12PositiveSupplyTL494ParameterTopologyBoost,Buck,Flyback,Forward,Full-Bridge,Half-Bridge,Push-PullControlmethodVoltageVCC(Min)(V)7VCC(Max)(V)40Dutycycle(Max)(%)45UVLOthresholdson/off(V)Frequency(Max)(kHz)300Operatingtemperaturerange(C)-40to85,0to70Gatedrive(Typ)(A)0.2FeaturesAdjustableSwitchingFrequency,DeadTimeControl,ErrorAmplifier,Multi-topologyRatingCatalogFeaturesCompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeInternalRegulatorProvidesaStable5-VReferenceSupplyWith5%ToleranceCircuitArchitectureAllowsEasySynchronizationAdvantagesTheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.TheTL494Cdeviceischaracterizedforoperationfrom0Cto70C.TheTL494Ideviceischaracterizedforoperationfrom40Cto85C.ApplicationsDesktopPCsMicrowaveOvensPowerSupplies:AC/DC,Isolated,WithPFC,90WServerPSUsSolarMicro-InvertersWashingMachines:Low-EndandHigh-EndE-BikesPowerSupplies:AC/DC,Isolated,NoPFC,90WPower:Telecom/ServerAC/DCSupplies:DualController:AnalogSmokeDetectorsSolarPowerInvertersTL494SimplifiedBlockDiagramTL494PackageandPinsPackagePinsSizePDIP(N)16181mm19.3x9.4SOIC(D)1659mm9.9x6SOP(NS)1680mm10.2x7.8TSSOP(PW)1622mm4.4x5FunctionalBlockDiagramWheretouseTL494TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology.TL494canbeusedtoprovideaconstantcurrentbyvaryingtheoutputvoltagetotheload.ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.SoifyouarelookingforanICtoproducePWMsignalsforcontrollingapowerswitchbasedonthecurrentflowingthroughthecircuit,thenthisICmightbetherightchoiceforyou.HowtouseTL494AtestcircuitfromtheTL494datasheetisshownbelow.NoninvertingpinsareconnectedtotheRefpinwhileinvertingpinsareconnectedtotheground.TestinputsaregiventoDTCandFEEDBACKpins.Externalcapacitorandresistorareconnectedtopin56tocontroltheoscillatorfrequency.Theerroramplifiercomparesasampleofthe5-VoutputtothereferenceandadjuststhePWMtomaintainaconstantoutputcurrentTL494TypicalApplicationSwitchingandControlSectionsInputPowerSourceError-AmplifierSectionCurrent-LimitingCircuitSoft-StartCircuitSwitchingCircuitPower-SwitchSectionFAQWhatisTL494?TL494isaPWMcontrollerICusedforpowerelectronicscircuits.Itcomprisesofon-chiptwoerroramplifiersanoscillatorwithadjustablefrequencyfeature,anoutputflip-flophavingpulsesteeringcontrol,andanoutputcontrolcircuitwithfeedback.WhatisthedetaileddescriptionofTL494?TheTL494deviceincorporatesallthefunctionsrequiredintheconstructionofapulse-width-modulation(PWM)controlcircuitonasinglechip.Designedprimarilyforpower-supplycontrol,thisdeviceofferstheflexibilitytotailorthepower-supplycontrolcircuitrytoaspecificapplication.TheTL494devicecontainstwoerroramplifiers,anon-chipadjustableoscillator,adead-timecontrol(DTC)comparator,apulse-steeringcontrolflip-flop,a5-V,5%-precisionregulator,andoutput-controlcircuits.Theerroramplifiersexhibitacommon-modevoltagerangefrom0.3VtoVCC2V.Thedead-timecontrolcomparatorhasafixedoffsetthatprovidesapproximately5%deadtime.Theon-chiposcillatorcanbebypassedbyterminatingRTtothereferenceoutputandprovidingasawtoothinputtoCT,oritcandrivethecommoncircuitsinsynchronousmultiple-railpowersupplies.Theuncommittedoutputtransistorsprovideeithercommon-emitteroremitter-followeroutputcapability.TheTL494deviceprovidesforpush-pullorsingle-endedoutputoperation,whichcanbeselectedthroughtheoutput-controlfunction.Thearchitectureofthisdeviceprohibitsthepossibilityofeitheroutputbeingpulsedtwiceduringpush-pulloperation.WhatareTL494productfeatures?CompletePWMPower-ControlCircuitryUncommittedOutputsfor200-mASinkorSourceCurrentOutputControlSelectsSingle-EndedorPush-PullOperationInternalCircuitryProhibitsDoublePulseatEitherOutputVariableDeadTimeProvidesControlOverTotalRangeWhatisPWMIC?TheTL494fixedfrequencyPWMControllercanbeusedforDCtoDCconversionregardlessofbuckorboosttopology....ThisICfeatureanoutputcontrolcircuit,aflipflop,adeadtimecomparator,twodifferenterroramplifiers,a5Vreferencevoltage,anoscillator,andaPWMcomparator.HowdoesPWMICwork?Asitsnamesuggests,pulsewidthmodulationspeedcontrolworksbydrivingthemotorwithaseriesofON-OFFpulsesandvaryingthedutycycle,thefractionoftimethattheoutputvoltageisONcomparedtowhenitisOFF,ofthepulseswhilekeepingthefrequencyconstant.WhichICisbetterforabuckconverter,TL494orUC3843?TheymainlydifferintypeofcontrolTL494=voltagemodecontrol(Oneloopcontrol).whileUC3843usescurrentmodecontrol(Nestedloopcontrol,withainner/fastcurrentloopandanotherouter/slowervoltageloop)Typicallyvoltagemodeareusedinmultipleoutputconverterswithgoodcross-regulation.CurrentmodewhenyouwanttoparallelmultipleconverterstomakeasingleconverterwithhighercurrentratingTL494isaverypopularIC.IfyouhavesimplerequirementsTL494isrecommendedHowdoIproperlysetthefeedbackpinonaTL494SMPSIC?Thefeedbackpinistheoutputofbotherroramplifiers,usedincomparingandadjustingtheoutputpulsewidthtotheDCcontrolvoltage.OnvariouscircuitsIhavelookedup,theop-ampconnectedtopins23areusedtosetthegainofthefeedbackloop,using2resistorswithoneresistorconnectingto2.5Vpotentialdivideron5Vreferencevoltage.Withtheotherconnectingtotheoutput(viasuitableisolation)Thegainappearstobesetat101,usinga51kfeedbackwith510ohmstothe2.5Vreference.Itisusedtocontrolthegainofthefeedbackvoltage.NoliteratureIhaveyetfound,givesanindicationonhowthisgainbeset,exceptagraphshowinganopenloopgainof1000,presumablythegainissetforthebeststability,althoughtherewillalsobeatimeconstant.WhyistherenofrequencycompensationrequiredinTIsTL494examplebuckregulatordesign(operationalamplifier,buckphase,shiftphase,margin,TL494,electronics)?ItsafixedfrequencyPWMcontrollerwithinternaldeadtimetimer.Frequencycompensationisnotrequired.Takealookatthedatasheet.HowtouseTL494?

MC33074

I.DesriptionInthefieldofmeasurementandcontrol,itisoftenencounteredthattheoutputsignalofthemonitoredobjectissmall,anditisdifficulttodirectlycollectit.Generally,itneedstobeamplifiedbeforeprocessing.Thisarticleintroducesamethodofimplementingasmallsignalacquisitionsystem.Thesmallestsystemisrealizedbyusingthesingle-chipSTC25A60S2withA/Dconversionfunctionandtheeasy-to-useamplifierAD620withpreciseamplificationfunction.Thesystemdesignandimplementationarediscussedandtheacquisitionisintroducedindetail.Theprocessofsmallsignal,andgivespracticalapplicationexamples,aswellastheapplicationofsmallsignalacquisitioninrelatedfields.AD620CatalogI.DesriptionII.AD620IntroductionIII.IntroductiontoSTC12C5A60S2IV.SystemHardwareDesign4.1SystemPrincipleBlockDiagram4.2PowerSupplyCircuitDesign4.3SignalConditioningCircuit4.4SystemDecouplingCircuit4.5RealizationofA/DConversion4.6Follow-upWorkV.PracticalApplicationVI.ConclusionFAQOrdering&QuantityII.AD620IntroductionAsamonolithicinstrumentamplifier,AD620haslowpowerconsumption,achipwithhighgainthroughexternalresistors,andfeatureslowinputdriftandtemperaturedrift.AD620isdevelopedfromthetraditionalthreeoperationalamplifiers,butsomeofthemainperformanceisbetterthanthedesignoftheinstrumentamplifiercomposedofthreeoperationalamplifiers,suchaswidepowersupplyrange(2.3~18V),smalldesignvolume,andverypowerconsumptionLow(themaximumpowersupplycurrentisonly1.3mA),soitissuitableforlow-voltage,low-powerapplications.Figure1SchematicdiagramofAD620principleThemonolithicstructureandlasercrystaladjustmentofAD620allowcircuitcomponentstobecloselymatchedandtracked,therebyensuringtheinherenthighperformanceofthecircuit.AD620isathree-op-ampintegratedinstrumentationamplifierstructure.Inordertoprotectthehighprecisionofgaincontrol,theinputtransistorprovidesasimpledifferentialbipolarinput,andusestheprocesstoobtainalowerinputbiascurrent.Throughtheinputstageinternalop-ampThefeedbacktokeepthecollectorcurrentoftheinputtransistorconstant,andtheinputvoltageisaddedtotheexternalgaincontrolresistorRG.ThetwointernalgainresistorsofAD620are24.7k8,sothegainequationis:G=49.4k/RG+1(1)Fortherequiredgain,theexternalcontrolresistancevalueis:RG=49.4/(G-1)k(2)III.IntroductiontoSTC12C5A60S2STC12C5A60S2isanewgeneration8051single-chipmicrocomputerwithA/Dconversionfunction.Theinstructioncodeisfullycompatiblewiththetraditional8051,butthespeedis8-12timesfaster.With8channelsofhigh-speed10-bitinputA/Dconversion(250k/s),itcanbeusedfortemperaturedetection,batteryvoltagedetection,keyscanning,spectrumdetection,etc.TheusercansetanychannelasA/Dconversion,andtheportsthatdonotneedtobeusedasA/DcancontinuetobeusedasI/Oports.Itscharacteristicsareasfollows:Figure2STC12C5A60S2(1)On-chipintegrated1280bytesRAM;(2)WithEEPROMfunction(STC12C5A62S2/AD/PWMwithoutinternalEEPROM);(3)Enhanced8051CPU,1T,singleclock/machinecycle,instructioncodeisfullycompatiblewithtraditional8051;(4)InternalintegratedMAX810dedicatedresetcircuit(whentheexternalcrystalisbelow12M,theresetpincanbedirectlyconnectedtothegroundwith1Kresistance);(5)Userapplicationspace8K/16K/20K/32K/40K/48K/52K/60K/62Kbytes;(6)ISP(In-SystemProgrammable)/IAP(In-ApplicationProgrammable),noneedforadedicatedprogrammer,noneedforadedicatedemulator,youcandownloadtheuserprogramdirectlythroughtheserialport(P3.0/P3.1),andonepiececanbecompletedinafewseconds;(7)STC12C5A60S2serieshavedualserialports,onlythosewiththeS2logosuffixhavedualserialports,RxD2/P1.2(canbesettoP4.2byregister),TxD2/P1.3(canbesettoP4.3byregister);(8)GeneralI/Oports(36/40/44),afterreset,theyare:quasi-bidirectionalport/weakpull-up(normal8051traditionalI/Oport),whichcanbesettofourmodes:quasi-bidirectionalport/weakPull-up,push-pull/strongpull-up,onlyinput/highimpedance,open-drain,eachI/Oportdrivecapacitycanreach20mA,butthewholechipshouldnotexceed120mA;(9)A/Dconversion,10-bitprecisionADC,8channelsintotal,conversionspeedupto250K/S(250,000timespersecond),universalfull-duplexasynchronousserialport(UART),becausetheSTC12seriesishigh-speed8051,canreusetimerorPCAsoftwaretorealizemultipleserialports.IV.SystemHardwareDesign4.1SystemPrincipleBlockDiagramGenerallyspeaking,beforethesignalisused,itneedstobefilteredandthenamplified,oramplifiedandthenfiltered,andthenobtained/perceivedbymeanssuchasA/D.Forsmallsignals,thesignalamplitudeisonlyafewmillivoltsorevensmaller.Iffilteredfirst,usefulsignalsmaybefilteredout.Therefore,inthiscase,youneedtoamplifyfirst,thenfilter,andthenperformA/Dconversionorotherprocessing.Accordingtothecharacteristicsofthissystem,theinterferenceinthesystemcanbeignored,sothesignalfilteringlinkisnotconsidered.Therefore,thesystemismainlyrealizedthroughthreeimportantlinks:signalextraction,signalamplification,andA/Dacquisition.Thedatageneratedinthethirdlinkcanguidepeoplesworkordisplayrelevantinformation.TheblockdiagramoftheentiresystemisshowninFigure3.Figure3Systemblockdiagram4.2PowerSupplyCircuitDesignAD620amplifiercanusesinglepowersupplyordualpowersupply,butwhenusingdualpowersupply,itsperformanceisbetterthansinglepowersupply.Inintegratedcircuitdesign,singlepowersupplyiseasytoimplement,butconsideringtheworkingperformanceofthechip,dualpowersupplyisusedinthissystem.UsetheICL7660Schiptoconvertanexternalsinglepowersupplyintoadualpowersupply.ICL7660Sisavoltageconversionchipthatcanrealizethefunctionofconvertingapositivevoltagetoanegativevoltage,anditsperipheralcircuitisrelativelysimple.ThespecificcircuitisshowninFigure4.Figure4PowersupplyimplementationschematicdiagramTheotherchipsinthesystemarepoweredbyasingle5Vpowersupply,andtheconnected5Vpowersupplycanbeusedwithoutanyprocessing,whichisnotdescribedhere.4.3SignalConditioningCircuitTheactualweaksignalisgenerallymVlevelorevensmaller.Beforeprocessing,itneedstobeamplifiedandthenA/Dcollected.AccordingtotheA/DfunctionofSTC12C5A60S2,itisnecessarytoaccuratelyamplifythesignaltoreachtheVlevel,sotheAD620amplifierisused.AD620hasagoodamplificationeffecton2inputdifferentialsignals.Inpracticalapplications,thesignalsaregenerallygeneratedbyelectricbridges.Inordertorealizesignalamplification,AD620needsanexternalresistor,whichdeterminestheamplificationfactortogetherwiththeinternalresistor.SupposethemagnificationisG,thenthereisthefollowingformula.G=(RG/R1)+1(1)canalsobewrittenasthefollowingformula:G=49.4k/RG+1(2)1)Intheformula,RGistheinternalresistanceofAD620,andR1istheexternalresistance.Itcanbeseenfromtheformulas(1)and(2)thatthesizeofRGintheformula(1)is49.4k.Theconditionedsignalisoutputthroughthe6-pinofAD620.Atthistime,itcanbedirectlyconnectedtotheA/Dconversionchiptorealizedatacollection.Itcanbereducedbythecorrespondingmultiplewhenusingit.TheprincipleofsignalconditioningisshowninFigure5.Figure5Signalconditioningcircuit4.4SystemDecouplingCircuitSincethesystemmainlyrealizessmallsignalamplificationandA/Dconversionafteramplification,thechipthatcompletestheA/Dfunctionofthissystem,namelySTC12C5A60S2,usesitsownworkingpowersupplyasthereferencevoltage.Inordertoensuretheconsistencyoftheconversionresults,itisnecessarytoensurethepowersupplyvoltagestability.Tofilterouttheinterferenceinthepowersupply,itcanbefilteredbymultiplecapacitorsinparallel.Afterthecapacitorsareconnectedinparallel,thecapacitancevalueincreases,buttheequivalentresistanceinsidethecapacitorisreducedduetotheparallelconnection,whichisbeneficialtoreducetheloss.Therefore,manycapacitorsareusedinparallel,andtherealizationprincipleisshowninFigure6.Figure6Powerdecouplingcircuit4.5RealizationofA/DConversionAsmentionedearlier,STC12C5A60S2isasingle-chipmicrocomputerwithA/Dconversionfunction,whichisconvenient,simple,andmulti-functional.ItsA/Dconversiononlyrequires90clockcycles(relatedtoitsoperatingfrequency)atthefastest.ThissystemUseittoachieveA/Dconversion.STC12C5A60S2usesportP1asan8-channelA/Dconversioninputinterface.Whenusingit,youonlyneedtosetitasananaloginterface.Bysettingthecorrespondingregister,theA/Dconversioncanbecompleted.Theunusedpinscanstillbeusedasordinarytubes.ThissystemrealizestheA/Dconversionofoneinputsignal,soitonlyneedstosetone.Inthissystem,P1.0portisusedasthesignalinputport.ThissystemrealizestheprincipleofA/DconversionasshowninFigure7.Figure7A/Dacquisitioncircuit4.6Follow-upWorkAftertheA/Dconversioniscompleted,dataanalysisisrequired.Generally,itcanbesenttotheuppercomputerthroughthecommunicationport(usuallyserialport),andthedataisprocessedbytheuppercomputer.Accordingtothedifferentcharacteristicsofthespecificsystem,thedataprocessingmethodsarealsodifferent,soitsnoneedtodiscussthemindetailhere.Table1ADconversiondataandactualdataAfterthesystemperformsA/Dconversiononsignalsofdifferentsizes,aseriesofactualdataandtheoreticaldataareobtained,asshowninTable1.DrawthecurveofA/DdatathroughExcel,andfoundthatthesystemA/Dconverterhasgoodlinearity.AsshowninFigure8.Figure8LinearityofA/DconverterV.PracticalApplicationThesmallsignalconditioning,A/Dconversion,andprocessingmethodsarediscussedinmoredetailabove.Thespecificapplicationisintroducedbelowthroughexamples.Asakindofsensingelement,resistancestraingaugeiscommonlyusedtomonitorthedeformationoftheobject.Generally,thestraingaugeisattachedtothesidepointofthecomponent.Afterthecomponentisstressed,duetothestrainofthemeasuringpoint,theresistancechanges,resultinginaweakvoltagechange.Thevoltagechangecanbecalculatedtoobtainthedeformationdegreeofthecomponent,soastoachievethepurposeofmonitoringtheconditionofthecomponentandguidetherelevantengineeringpersonneltodealwithit.Thissystemcanbeappliedtothevoltagegeneratedbytheelectricbridge.AschematicdiagramoftheelectricbridgeisshowninFigure9.Inthefigure,R4,R3,R1,andR2arethefourarmsofthebridge,R4andR3arefixedresistancesofimpedance,andR1andR2areinOneisaresistorwhoseresistancevaluechangesafterbeingstressed.R4andR3havethesameresistancevalue,andR1andR2havethesameresistancevaluewhentheyarenotstressed.Inthecaseofnoforce,thetwopointsofthebridge3and4areequipotential,thatis,thepotentialdifferenceis0.IfitisinputasAD620,theinputsignalisconsideredtobe0,andthebridgeissaidtobebalancedatthistime.WhentheforceofR1orR2changes,theresultofthechangeisreflectedinitsresistancevalue,whichcanbeobtainedbyOhmslaw.Thepotentialatpoints3and4isdifferent,thatis,thereisapotentialdifference.Atthistime,thebridgeisoutofbalance,butatthistimeThesignalisveryweakandcannotbecollecteddirectly.Therefore,thesignalisamplifiedthroughthesignalconditioningcircuitmentionedinthearticle,thatis,points3and4inthebridgeareconnectedtopins2and3ofAD620,afteramplification,thenA/Dacquisitionisperformed.Figure9SchematicdiagramofelectricbridgeThissystemusesasimpleelectricbridgebuiltbyitselfduringsimulation,asshowninFigure10.Figure10SimpleelectricbridgeByadjustingR2inthefigure,differentweaksignalsaregenerated,andthesimplebridge1and2areconnectedtothesignalconditioningcircuit,andthenafterA/Dconversion,weaksignalacquisitioncanberealized.The1,2endsofthesimpleelectricbridgecorrespondtothe3and4endsinthefigure.Inthissimulation,adjustR2togenerateabout5.35mVatbothendsof1,2andadjusttheexternalresistanceinthesignalconditioningcircuitto160.7.Thecalculatedmagnificationisabout308.4times,andtheA/Dreferencevoltageis4.256VBymeasuringtheoutputofAD620,itcanbeobtainedthatthevoltageis1.645V,andthemagnificationfactorG=1.647V/5.35mV308canbecalculated.Itcanbeseenthatthemagnificationeffectisgood(afterremovingthemagnificationeffect,theerrorisonlynVlevel).ThroughmultipleA/Dconversions,thereturnedresultsareallaround0x018B,whichprovesthatthesystemhashighcredibility(ithasbeenusedinactualsystems).VI.ConclusionThisarticledescribesindetailthedesignandimplementationofsmallsignalacquisitionsystemsfromchipselection,circuitdesign,etc.,suchas8-bitsingle-chipSTC12C5A60S2asthecontrollerandA/Dconverter;AD620asthemainchipofthesignalconditioningcircuit;electricbridgeprincipleetc.Throughthetest,thecircuithasrealizeditsfunctionwell,andithasaccomplishedtheexpectedgoalexcellentlyintheactualsystem,whichhascertainpracticalvalue.FAQWhatisAD620?AD620isalow-cost,high-precisioninstrumentationamplifier.Itonlyrequiresanexternalresistortosetthegain.Thegainrangeis1to10,000.CanIchangeAD620toAD623whenmakingMCUproducts?BothAD620andAD623aresingleinstrumentationamplifiers,andthepinarrangementisexactlythesame.Themaindifferenceis:AD620mustusepositiveandnegativepowersupplies,AD623canbeapositiveandnegativepowersupplyorasinglepowersupply.IftheoriginalboardisAD620,youcanreplaceitwith623;iftheoriginalboardisAD623,youmaynotbeabletoreplaceitwith620(itdependsonwhetherthepowersupplyoftheoriginalboardcircuitisdualpowersupplyorsinglepowersupply).AfterreplacingAD620andAD623insingle-chipproducts,theprogramcanworknormallywithoutmodification.WhatisthedifferencebetweenAD620BRandAD620AN?Theirpackagesaredifferent.WhatistheoutputresistanceofAD620?Howtoadjustit?AD620isakindoflowpowerconsumptioninstrumentamplifier,itsoutputresistanceisabout10K,thisistheinherentcharacteristicofthischip,generallyitisdifficulttoadjust.Ifyouhaverequirementsforoutputresistance,youcangenerallyuseanexternalcircuittosolveit.IsAD620apositivephaseamplificationorareversephaseamplification?AD620isaninstrumentamplifier,theoutputvoltageis[(Vin+)-(Vin-)]*gain.Ifthedesiredsignalis(Vin+)-(Vin-),thegainispositive,whichisequivalenttopositiveamplification.Conversely,ifthedesiredsignalis(Vin-)-(Vin+),thegainisequivalenttonegative,whichisequivalenttoreverseamplification.Whatisaninstrumentationamplifier?Instrumentationamplifier,animprovementofthedifferentialamplifier,hasaninputbuffer,doesnotrequireinputimpedancematching,sothattheamplifierissuitableformeasurementandelectronicinstruments

DescriptionThe2N7000isaN-ChannelEnhancementModeFieldEffectTransistor,a.k.a.MOSFETforvoltagecontrolledsmallsignalswitching.2N7000NChannelEnhancementModeMOSFETSwitchCircuitBasicsCatalogDescription2N7000Pinout2N7000Parameters2N7000Features2N7000Applications2N7000Advantage2N7000SwitchingWaveformsandTestCircuit2N7000PackageInformation2N7000PopularitybyRegion2N7000AlternativesHowtouse2N7000Wheretouse2N7000ProductManufacturerFAQOrdering&Quantity2N7000PinoutPinNumberPinNameDescription1SourceCurrentflowsoutthroughSource2GateControlsthebiasingoftheMOSFET3DrainCurrentflowsinthroughDrain2N7000ParametersConfigurationSINGLEWITHBUILT-INDIODEContinuousDrainCurrent(ID)200mADrainCurrent-Max(ID)0.2ADraintoSourceResistance5RDraintoSourceVoltage(Vdss)60VDrain-sourceOnResistance-Max5DSBreakdownVoltage-Min60VElementConfigurationSingleFeedbackCap-Max(Crss)5pFFETTechnologyMETAL-OXIDESEMICONDUCTORGatetoSourceVoltage(Vgs)30VHeight5.33mmJEDEC-95CodeTO-92JESD-30CodeO-PBCY-T3LeadFreeLeadFreeLength5.21mmManufacturerMicrochipTechnologyIncManufacturerPartNumber2N7000-GP003MaxPowerDissipation1WNumberofChannels1NumberofElements1NumberofTerminals3OperatingModeENHANCEMENTMODEOperatingTemperature-Max150COperatingTemperature-Min-55CPackageTO-92-3PartLifeCycleCodeActivePolarity/ChannelTypeN-CHANNELReachComplianceCodeCompliantREACHSVHCNoSVHCRiskRank5.56SurfaceMountNOTerminalFormTHROUGH-HOLETerminalPositionBOTTOMTransistorApplicationSWITCHINGTransistorElementMaterialSILICONVoltageRating(DC)60VWeight0.00776ozWidth4.19mm2N7000FeaturesFreefromsecondarybreakdownLowpowerdriverequirementEaseofparallelingLowCISSandfastswitchingspeedsExcellentthermalstabilityIntegralsource-draindiodeHighinputimpedanceandhighgain2N7000ApplicationsMotorcontrolsConvertersAmplifiersSwitchesPowersupplycircuitsDrivers(relays,hammers,solenoids,lamps,memories,displays,bipolartransistors,etc.)The2N7000hasbeenreferredtoasaFETlingtonandasanabsolutelyidealhackerpart.ThewordFETlingtonisareferencetotheDarlington-transistor-likesaturationcharacteristic.Atypicaluseofthesetransistorsisasaswitchformoderatevoltagesandcurrents,includingasdriversforsmalllamps,motors,andrelays.Inswitchingcircuits,theseFETscanbeusedmuchlikebipolarjunctiontransistors,buthavesomeadvantages:highinputimpedanceoftheinsulatedgatemeansalmostnogatecurrentisrequiredconsequentlynocurrent-limitingresistorisrequiredinthegateinputMOSFETs,unlikePNjunctiondevices(suchasLEDs)canbeparalleledbecauseresistanceincreaseswithtemperature,althoughthequalityofthisloadbalanceislargelydependentontheinternalchemistryofeachindividualMOSFETinthecircuitThemaindisadvantagesoftheseFETsoverbipolartransistorsinswitchingarethefollowing:susceptibilitytocumulativedamagefromstaticdischargepriortoinstallationcircuitswithexternalgateexposurerequireaprotectiongateresistororotherstaticdischargeprotectionNon-zeroohmicresponsewhendriventosaturation,ascomparedtoaconstantjunctionvoltagedropinabipolarjunctiontransistor2N7000AdvantageTheSupertex2N7000isanenhancement-mode(normallyoff)transistorthatutilizesaverticalDMOSstructureandSupertexswell-provensilicon-gatemanufacturingprocess.Thiscombinationproducesadevicewiththepowerhandlingcapabilitiesofbipolartransistors,andthehighinputimpedanceandpositivetemperaturecoefficientinherentinMOSdevices.CharacteristicofallMOSstructures,thisdeviceisfreefromthermalrunawayandthermally-inducedsecondarybreakdown.SupertexsverticalDMOSFETsareideallysuitedtoawiderangeofswitchingandamplifyingapplicationswhereverylowthresholdvoltage,highbreakdownvoltage,highinputimpedance,lowinputcapacitance,andfastswitchingspeedsaredesired.2N7000SwitchingWaveformsandTestCircuit2N7000PackageInformation3-LeadTO-92PackageOutline(N3)FrontView3-LeadTO-92PackageOutline(N3)SideView3-LeadTO-92PackageOutline(N3)BottomView2N7000PopularitybyRegion2N7000AlternativesManufacturerManufacturerPartNo.LifecycleStatusIndicatorMicrochipSupertex2N7000-GVolumeProductionHowtouse2N7000AMosfethasthreeterminals:Drain,SourceandGate.ThecurrentalwaysentersthroughtheDrainandleavesthroughtheSource.TheGatepinactsasaswitchtoturntheMosfetonoroff.IftheGateisconnectedtoground,theMosfetisswitchedoff,i.e.thereisnoconnectionbetweentheDrainandtheSource(open).IftheGateissuppliedwithitssourcevoltage(VGS)thentheMOSFETwillbeON,i.e.theDrainandSourcepinswillbeconnectedtogether(Closed).Thus,bycontrollingthevoltage(VGS),wecanswitchtheMOSFET,makingtheMOSFETavoltage-controlleddevice.Thegate-sourcevoltage(VGS)isacriticalparameterwhenusingthetransistor.Forthistransistor,theVGSis20V,sowhenwesupplythisvoltage,theMOSFETwillbecompletelyclosed.Anyvaluebetween20VcausestheMOSFETtopartiallyclose,creatingapartialconnection.TheloadswitchedbytheMOSFETcanreach60V(VDS)andcanconsumeupto200mA(ID).GivenbellowisaverysimplecircuitunderneaththatusesthisMOSFETtocontrola24V2Aloadmotor.Thecurrentandvoltagevaluescanalsobeobservedwhentheswitchisclosedandopen.AsweknowthatthevoltageofthegridsourceofthisMosfetis20V,weused20VtoturnontheMOSFET.Whenthegateswitchisopen,theMosfetsgatepinmustbeconnectedtogroundtocuttheload,soweuseda10KresistortoturnofftheMOSFETafterturningiton.TheRGresistorisacurrentlimitingresistorthatlimitstherequiredgridcurrent.IftheloadcontrolledbytheMOSFETisaninductiveloadlikethemotorwehaveusedhere,thenitismandatorytouseaflywheeldiodetosafelydischargetheloadaccumulatedbytheinductivecoil.Wheretouse2N70002N7000isasmallN-channelMOSFET.MOSFETsareelectronicpowerswitches,justliketransistors,butwithahighercurrentandvoltagerating.The2N7000MOSFETcanbeusedtoswitchloadsthatoperateonlessthan60V(VDS)and200mA(ID).ThismosfetcomesinacompactTO-92packageandhasathresholdvoltageof3V,soifyouarelookingforasmallmosfettoswitchaload,thisICmightberightforyou.ProductManufacturerMicrochipTechnologyInc.isaleadingproviderofmicrocontrollerandanalogsemiconductors,providinglow-riskproductdevelopment,lowertotalsystemcostandfastertimetomarketforthousandsofdiversecustomerapplicationsworldwide.HeadquarteredinChandler,Arizona,Microchipoffersoutstandingtechnicalsupportalongwithdependabledeliveryandquality.FAQWhatisa2n7000Mosfet?2N7000isasmallsignalN-channelMOSFET.MOSFETsarepowerelectronicswitchesjustliketransistors,butwithahighercurrentandvoltagerating.The2N7000MOSFETcanbeusedtoswitchloadswhichoperatesonlessthan60V(VDS)and200mA(ID).Whatisamaximumoperatingvoltageforthe2n7002transistor?The2N7002isalogiclevelMOSFETwithalowon-stateresistance.Themosfethasalowgatetosourcethresholdvoltageof2.1Vtypicallythismakesthemosfetsuitableevenfor3.3Vapplicationcircuits.WhatisMosfetgatethresholdvoltage?ThethresholdvoltagerepresentsthevoltageatwhichtheMOSFETstartstoturnon,whilstthemaximumgate-sourcevoltageisthemaximumgate-sourcevoltagethattheMOSFETcanwithstandsafely.WhatisanchannelMosfet?TheN-ChannelMOSFEThasanN-channelregionlocatedinbetweenthesourceanddrainterminals.Itisafour-terminaldevicehavingtheterminalsasgate,drain,source,body.InthistypeofFieldEffectTransistor,thedrainandsourceareheavilydopedn+regionandthesubstrateorbodyareofP-type.DescriptionDS18B20isatemperaturesensorofMaxim.Thesingle-chipmicrocomputercancommunicatewithDS18B20through1-Wireprotocolandfinallyreadthetemperature.Thehardwareinterfaceofthe1-Wirebusisverysimple,justconnectthedatapinofDS18B20toanIOportofthemicrocontroller.ThisVideoIntroducesDS18B20withDatasheetCatalogDescriptionDocumentandMediaDS18B20PinoutParametersAdvantageFeaturesApplicationsDS18B20CircuitSchematicDS18B20TemperatureSensorDataDS18B20BlockDiagramHowtousetheDS18B20SensorWheretouseDS18B20SensorProductManufacturerFAQOrdering&QuantityDocumentandMediaComponentDatasheetDS18B20DatasheetDS18B20PinoutPinNameFunctionSOSOPTO-921,2,6,7,82,3,5,6,7-N.C.NoConnection383VDDOptionalVDD.VDDmustbegroundedforoperationinparasitepowermode.412DQDataInput/Output.Open-drain1-Wireinterfacepin.Alsoprovidespowertothedevicewhenusedinparasitepowermode(seethePoweringtheDS18B20section.)541GNDGroundParametersAccuracy(C)0.5ChannelsOneInterface1-WireMultiDroppableYesOper.Temp.(C)-55to+125Package/PinsSOIC(N)/8,TO92/3,UMAX/8ParasitePwr.YesPartNumberDS18B20SensorTypeLocalTemp.Resolution(bits)9,10,11,12Temp.Thresh.Programmable(NV)AdvantageTheDS18B20digitalthermometerprovides9-bitto12-bitCelsiustemperaturemeasurementsandhasanalarmfunctionwithnonvolatileuser-programmableupperandlowertriggerpoints.TheDS18B20communicatesovera1-Wirebusthatbydefinitionrequiresonlyonedataline(andground)forcommunicationwithacentralmicroprocessor.Inaddition,theDS18B20canderivepowerdirectlyfromthedataline(parasitepower),eliminatingtheneedforanexternalpowersupply.EachDS18B20hasaunique64-bitserialcode,whichallowsmultipleDS18B20stofunctiononthesame1-Wirebus.Thus,itissimpletouseonemicroprocessortocontrolmanyDS18B20sdistributedoveralargearea.ApplicationsthatcanbenefitfromthisfeatureincludeHVACenvironmentalcontrols,temperaturemonitoringsystemsinsidebuildings,equipment,ormachinery,andprocessmonitoringandcontrolsystems.FeaturesUnique1-WireInterfaceRequiresOnlyOnePortPinforCommunicationReduceComponentCountwithIntegratedTemperatureSensorandEEPROMMeasuresTemperaturesfrom-55Cto+125C(-67Fto+257F)0.5CAccuracyfrom-10Cto+85CProgrammableResolutionfrom9Bitsto12BitsNoExternalComponentsRequiredParasiticPowerModeRequiresOnly2PinsforOperation(DQandGND)SimplifiesDistributedTemperature-SensingApplicationswithMultidropCapabilityEachDeviceHasaUnique64-BitSerialCodeStoredinOn-BoardROMFlexibleUser-DefinableNonvolatile(NV)AlarmSettingswithAlarmSearchCommandIdentifiesDeviceswithTemperaturesOutsideProgrammedLimitsAvailablein8-PinSO(150mils),8-PinSOP,and3-PinTO-92PackagesApplicationsConsumerProductsIndustrialSystemsThermallySensitiveSystemsThermometersThermostaticControlsDS18B20CircuitSchematicDS18B20TemperatureSensorDataDS18B20canachievethehighest12-bittemperaturestoragevaluethroughprogramming.Thetemperaturestoragevalueisstoredintheregisterinacomplementformat.Thereare2bytesintotal,LSBisthelowbyteandMSBisthehighbyte.Amongthem,MSbisthehighbitofthebyte,andLSbisthelowbitofthebyte.Forbinarynumbers,themeaningofthetemperaturerepresentedbyeachofthemisexpressed.Amongthem,Srepresentsthesignbit,andthelower11bitsareallpowersof2,whichareusedtorepresentthefinaltemperature.ThetemperaturemeasurementrangeofDS18B20isfrom-55degreesto+125degrees.Themanifestationoftemperaturedatahaspositiveandnegativetemperatures.Eachnumberintheregisterisdistributedlikethescaleofacaliper.Thelowestbitofthebinarynumberchanges1,whichrepresentsthemappingrelationshipofatemperaturechangeof0.0625degrees.Whenthetemperatureis0℃,thecorrespondinghexadecimalnumberis0x0000.Whenthetemperatureis125℃,thecorrespondinghexadecimalnumberis0x07D0.Whenthetemperatureisminus55℃,thecorrespondinghexadecimalnumberis0xFC90.Conversely,whenthenumberis0x0001,thetemperatureis0.0625℃.DS18B20BlockDiagramHowtousetheDS18B20SensorThesensorworkswiththemethodof1-Wirecommunication.Itrequiresonlythedatapinconnectedtothemicrocontrollerwithapullupresistorandtheothertwopinsareusedforpowerasshownbelow.Thepull-upresistorisusedtokeepthelineinhighstatewhenthebusisnotinuse.Thetemperaturevaluemeasuredbythesensorwillbestoredina2-byteregisterinsidethesensor.Thisdatacanbereadbytheusingthe1-wiremethodbysendinginasequenceofdata.Therearetwotypesofcommandsthataretobesenttoreadthevalues,oneisaROMcommandandtheotherisfunctioncommand.TheaddressvalueofeachROMmemoryalongwiththesequenceisgiveninthedatasheetbelow.Youhavetoreadthroughittounderstandhowtocommunicatewiththesensor.IfyouareplanningtointerfaceitwithArduino,thenyouneednotworryaboutallthese.Youcandevelopthereadilyavailablelibraryandusethein-builtfunctionstoaccessthedata.WheretouseDS18B20SensorTheDS18B20isa1-wireprogrammableTemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.Itcanmeasureawiderangeoftemperaturefrom-55Cto+125withadecentaccuracyof5C.EachsensorhasauniqueaddressandrequiresonlyonepinoftheMCUtotransferdatasoitaverygoodchoiceformeasuringtemperatureatmultiplepointswithoutcompromisingmuchofyourdigitalpinsonthemicrocontroller.ProductManufacturerMaximIntegratedprovideseaseofdesign,andspeedstimetomarket,throughanalogintegration.ThecompanysanalogICsofferextrafeaturesandfunctionalitycarefullydesignedtostreamlinecircuitandsimplifydesign.LooktoMaximforsolutionsforconsumerelectronics,personalcomputersandperipherals,mobiledevices,wirelessandfibercommunications,testequipment,instrumentation,videodisplays,andautomotiveapplications.Maximsanalogandmixed-signalsolutionsincludedataconverters,interfacecircuits,power,RFwirelesscircuits,clocksandoscillators,microcontrollers(MCUs),operationalamplifiers(opamps),andsensors.FAQWhatisDS18B20temperaturesensor?TheDS18B20isa1-wireprogrammabletemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.HowdoestheDS18B20work?Itworksontheprincipleofdirectconversionoftemperatureintoadigitalvalue.IsDS18B20athermistor?Athermistorisathermalresistor-aresistorthatchangesitsresistancewithtemperature....Thermistorshavesomebenefitsoverotherkindsoftemperaturesensorssuchasanalogoutputchips(LM35/TMP36)ordigitaltemperaturesensorchips(DS18B20)orthermocouples.HowaccurateisDS18B20?TheDS18B20readswithanaccuracyof0.5Cfrom-10Cto+85Cand2Caccuracyfrom-55Cto+125C.Whatisds1820?TheDS18B20isonetypeoftemperaturesensoranditsupplies9-bitto12-bitreadingsoftemperature....Thecommunicationofthissensorcanbedonethroughaone-wirebusprotocolwhichusesonedatalinetocommunicatewithaninnermicroprocessor.HowdoIconnectmyDS18B20tomyRaspberryPi?OnceyouveconnectedtheDS18B20,powerupyourPiandlogin,thenfollowthesestepstoenabletheOne-Wireinterface:1.Atthecommandprompt,entersudonano/boot/config.txt,thenaddthistothebottomofthefile:2.dtoverlay=w1-gpio.3.ExitNano,andrebootthePiwithsudoreboot.WhatistheworkingprincipleofDS18B20?TheDS18B20DigitalThermometerprovides9to12-bit(configurable)temperaturereadingswhichindicatethetemperatureofthedevice.Itcommunicatesovera1-Wirebusthatbydefinitionrequiresonlyonedataline(andground)forcommunicationwithacentralmicroprocessor.Inadditionitcanderivepowerdirectlyfromthedataline(parasitepower),eliminatingtheneedforanexternalpowersupply.ThecorefunctionalityoftheDS18B20isitsdirect-to-digitaltemperaturesensor.Theresolutionofthetemperaturesensorisuser-configurableto9,10,11,or12bits,correspondingtoincrementsof0.5C,0.25C,0.125C,and0.0625C,respectively.Thedefaultresolutionatpower-upis12-bit.WheretouseDS18B20Sensor?TheDS18B20isa1-wireprogrammableTemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.Itcanmeasureawiderangeoftemperaturefrom-55Cto+125withadecentaccuracyof5C.EachsensorhasauniqueaddressandrequiresonlyonepinoftheMCUtotransferdatasoitaverygoodchoiceformeasuringtemperatureatmultiplepointswithoutcompromisingmuchofyourdigitalpinsonthemicrocontroller.HowconnectDS18B20toArduino?FirstplugthesensoronthebreadboardtheconnectitspinstotheArduinousingthejumpersinthefollowingorder:pin1toGND;pin2toanydigitalpin(pin2inourcase);pin3to+5Vor+3.3V,attheendputthepull-upresistor.OnanATMega328P,whyisaDS18B20temperaturesensorreturningincorrecttemperaturevalues?Severalpossibilities:1.Ifitisjustreadingalittlehigh,itmightbecausedbyselfheating.Addaheatsinkand/ormakemeasurementslessfrequently.2.Especiallyifthevaluesarereallywhacky,itmightbecodewitherrorsormis-wiring.Useapublishedsketchtocheckoperation.3.TheDS18B20mightbedefective.Tryanother.4.Itsaccurateto0.5C.Areyouexpectingittobemoreaccurate(likedowntotheLSBofthereadvalue)?

IDescriptionFirst,thisblogwillintroducethe1wiredigitaltemperaturesensorDS18B20.Wemainlyintroduceitsstructure,characteristicsandworkingprinciplehere.Second,wewillintroduceatemperaturemeasurementsystembasedonDS18B20andAT89S52microcontroller.Herewemainlyintroduceitshardwarestructureandassembler.Third,therewillbepartofthesourceprogramthatisdetailedanalyed.Finally,theblogalsoexplainshowitperformstemperaturemeasurementintheagriculturalfield.Thetemperaturemeasuringdevicehasaseriesofadvantages.Suchas:highdisplayaccuracy,lowprice,simplestructure,convenientexpansionandwideapplication.DS18B20TemperatureSensorTutorialCatalogIDescriptionIIIntroductionIIIDS18B20Overview3.1DS18B20Advantages3.2DS18B20Features3.3DS18B20InternalStructureIVDS18B20MCUTemperatureMeasurementDevice4.1CompositionofSystemHardware4.2DesignofInterfaceVSoftwareDesignVIApplicationinAgriculturalProduction6.1TemperatureofMildew6.2TemperatureofAgriculturalProducts6.3TemperatureDetectioninGreenhouses6.4TemperatureofSoilVIIConclusionFAQOrdering&QuantityIIIntroductionWhatistemperature?Whataretherolesoftemperature?Temperatureisaphysicalquantitythatcharacterizesthedegreeofcoolingofanobject,anditisalsoabasicenvironmentalparameter.Inagro-industrialproductionanddailylife,themeasurementandcontroloftemperaturealwaysoccupyanextremelyimportantposition.Atpresent,atypicaltemperaturemeasurementandcontrolsystemconsistsofthefollowingparts:Analogtemperaturesensor;A/Dconversioncircuit;MCU.However,theanalogsignaloutputbytheanalogtemperaturesensorhastobeconverted.Itcaninterfacewithmicroprocessorssuchassingle-chipmicrocomputersonlyafterobtainingdigitalsignalsthroughtheA/Dconversionlink.Therefore,thehardwarecircuitstructureiscomplicatedandthecostishigh.ButDS18B20canhelpsolvethisproblem.Thenew1wiredigitaltemperaturesensorrepresentedbyDS18B20integratestemperaturemeasurementandA/Dconversion,anddirectlyoutputsdigitalquantities.Thestructureoftheinterfacecircuitwiththesingle-chipmicrocomputerissimple,anditiswidelyusedintheoccasionswithlongdistanceandmanynodes.Therefore,DS18B20hasstrongpromotionandapplicationvalue.IIIDS18B20Overview3.1DS18B20AdvantagesDS18B20type1wireintelligenttemperaturesensorproducedbyDALLASSemiconductorCompany.Itbelongstoanewgenerationofintelligenttemperaturesensorsadaptedtomicroprocessors.Comparedwiththetraditionalthermistor,ithasthefollowingadvantages:Itcandirectlyreadthemeasuredtemperature;Thereadingmodeof9-12digitscanberealizedthroughsimpleprogrammingaccordingtoactualrequirements;Itcanalsocomplete9-bitand12-bitdigitalquantitieswithin93.75msand750ms,respectively,withamaximumresolutionof0.0625C;ToreadorwritetheinformationofDS18B20,onlyoneportline(1wireinterface)isrequiredtoreadandwrite.3.2DS18B20FeaturesUnique1-WireInterfaceRequiresOnlyOnePortPinforCommunicationReduceComponentCountwithIntegratedTemperatureSensorandEEPROMMeasuresTemperaturesfrom-55Cto+125C(-67Fto+257F)0.5CAccuracyfrom-10Cto+85CProgrammableResolutionfrom9Bitsto12BitsNoExternalComponentsRequiredParasiticPowerModeRequiresOnly2PinsforOperation(DQandGND)SimplifiesDistributedTemperature-SensingApplicationswithMultidropCapabilityEachDeviceHasaUnique64-BitSerialCodeStoredinOn-BoardROMFlexibleUser-DefinableNonvolatile(NV)AlarmSettingswithAlarmSearchCommandIdentifiesDeviceswithTemperaturesOutsideProgrammedLimitsAvailablein8-PinSO(150mils),8-PinSOP,and3-PinTO-92Packages3.3DS18B20InternalStructureDS18B20adopts3-pinPR-35packageor8-pinSOICpackage.ItsDS18B20externalshapeandpindiagramareshowninFigure1.TheDS18B20internalstructureblockdiagramisshownasinFigure2.Thestructureof64-bitflashROMisshowninFigure3.Figure1.DS18B20PinoutFigure2.DS18B20InternalStructureFigure3.64bFlashROMStructureIVDS18B20MCUTemperatureMeasurementDevice4.1CompositionofSystemHardwareTheDS18B20single-chipmicrocomputerintelligenttemperaturemeasurementdeviceismainlycomposedofDS18B20temperaturesensor,AT89S52,displaymoduleandpowermodule,asshowninFigure4.Themaintechnicalindicatorsoftheproductare:MeasuringRange(℃):-55.0~+125.0MeasurementAccuracy(℃):0.1ResponseTime(s):1.5Figure4.SystemStructureDiagramThesystemusesDS18B20asatemperaturesensor.Theone-chipcomputerAT89S52ofATMELCompanyservesastheprocessor.Temperaturedisplayandlight-emittingdiodeastemperaturecontroloutputunit.Thewholesystemstrivestohaveasimplestructureandperfectfunctions.Theworkingprincipleofthesystemisasfollows:AfterDS18B20carriesonthefieldtemperaturemeasurement,themeasureddataissenttotheP3.5portofAT89S52.Thetemperaturevalueisdisplayedafterbeingprocessedbythemicrocontroller.Then,thistemperaturevalueiscomparedwiththeupperlimitofthesetalarmtemperature.Ifitishigherthanthesetupperlimit,theyellowLEDlightsup.ThemaincircuitdiagramofthesystemisshownasinFig.5.Figure5.DS18B20TemperatuerMeasurementDevice4.2DesignofInterfaceThereare2waystoconnectDS18B20tothehardwareofthemicrocontroller:Vccisconnectedtoexternalpowersupply,GNDisgrounded,andI/OisconnectedtotheI/Olineofthemicrocontroller;Useparasiticpowersupply,UDDandGNDaregroundedatthistime,andI/OisconnectedtoMCUI/O.Regardlessofthe1stor2ndpowersupplymode,theI/Olinemustbeconnectedtoapull-upresistorofabout4.7k.Figure6showsatypicalconnectionbetweenDS18B20andamicroprocessor.InFigure6(a),DS18B20adoptsparasiticpowersupply,anditsVDDandGNGterminalsarebothgrounded;InFigure6(b),theDS18B20usesanexternalpowersupply,anditsVDDterminalusesa3~5.5Vpowersupply.ThissystemadoptsthewiringmodeshowninFigure6(b),thatis,theworkingmodeofexternalpowersupply.TheactualconnectionpictureofthesystemisshowninFigure6.Figure6.PhysicalDiagramofSystemConnectionVSoftwareDesignItisworthnotingthatDS18B20hasveryhighrequirementsontwoaspects:timingandelectricalparameters.Therefore,theworkflowofthemainCPUaccessingtheDS18B20throughthesingle-businterfacemustfollowastrictoperatingsequence:first,initializetheDS18B20;second,sendROMcommands;andthen,sendfunctioncommands.Wecantakealookatthefollowingpartofthesourceprogramisasfollows:ORG0000HAJMPMAIN;StatementofMCUmemoryallocation!TEMPER_LEQU29H;usedtosavethelower8bitsofthereadtemperatureTEMPER_HEQU28H;usedtosavetheupper8bitsofthereadtemperatureFLAG1EQU38H;WhethertheDS18B20flagisdetectedPNFLAGEQU68H;DatapositiveandnegativeflagA_BITEQU20H;thesingledigitofthedigitaltubestoresthememorylocationB_BITEQU21H;ThetendigitsofthedigitaltubestorethememorylocationC_BITEQU22H;ThedecimalplacesofthedigitaltubestorethememorylocationT_INTEGEREQU26H;TheintegerpartafterFORMAT,whichintegratestwobytesoftemperatureintoonebyteT_DFEQU27H;ThedecimalfractionafterFORMAT,thedecimalfractionofnibbletemperature(therearelowfourdigits)MAIN:LCALLGET_TEMPER;CallthetemperaturereadingsubroutineLCALLT_FORMAT;Formattheread2bytetemperatureLCALLALARM;callthealarmsubroutineLCALLDISPLAY;callthedigitaltubedisplaysubroutineLCALLD1S;testafteradelayof0.5secondsAJMPMAIN;thisistheDS18B20resetinitializationsubroutineINIT_1820:SETBP3.5NOPCLRP3.5;thehostsendsoutaresetlowpulsewithadelayof537microsecondsMOVR1,#2TSR1:MOVR0,#250DJNZR0,$DJNZR1,TSR1SETBP3.5;thenpullupthedatalineNOPNOPNOPMOVR0,#25HTSR2:JNBP3.5,TSR3;waitingforDS18B20responseDJNZR0,TSR2;delayLJMPTSR4TSR3:SETBFLAG1;SettheflagbittoindicatethatDS1820existsLJMPTSR5TSR4:CLRFLAG1;cleartheflagbit,indicatingthatDS1820doesnotexistLJMPTSR7TSR5:MOVR0,#120TSR6:DJNZR0,TSR6;timingrequiresaperiodofdelayTSR7:SETBP3.5RET;readthetemperaturevalueafterconversionGET_TEMPER:;SETBP3.5LCALLINIT_1820;firstresetDS18B20JBFLAG1,TSS2RET;DeterminewhetherDS1820exists?IfDS18B20doesnotexistThenreturnTSS2:MOVA,#0CCH;skipROMmatchingLCALLWRITE_1820MOVA,#44H;IssuetemperatureconversioncommandLCALLWRITE_1820LCALLDISPLAYLCALLINIT_1820;resetbeforereadingtemperatureMOVA,#0CCH;SkipROMmatchingLCALLWRITE_1820MOVA,#0BEH;IssuereadtemperaturecommandLCALLWRITE_1820LCALLREAD_18200;savethereadtemperaturedatato28H/29HRET;WriteDS18B20subroutine(withspecifictimingrequirements)WRITE_1820:MOVR2,#8;atotalof8bitsofdata;CLRCWR1:CLRP3.5MOVR3,#6DJNZR3,$RRCAMOVP3.5,CMOVR3,#23DJNZR3,$SETBP3.5NOPDJNZR2,WR1SETBP3.5RET;readtheprogramofDS18B20,readtwobytesoftemperaturedatafromDS18B20READ_18200:MOV36H,#2;SetthehighandlowtemperatureReadfromDS18B20MOVR1,#29H;thelowbitisstoredin29H(TEMPER_L),thehighbitDeposit28H(TEMPER_H)RE00:MOVR2,#8;Thereare8bitsofdataRE01:;CLRCSETBP3.5NOPNOPCLRP3.5NOPNOPNOPSETBP3.5MOVR3,#9RE10:DJNZR3,RE10MOVC,P3.5MOVR3,#23RE20:DJNZR3,RE20RRCADJNZR2,RE01MOV@R1,ADECR1DJNZ36H,RE00RET;-----Integratethetwo-bytetemperaturereadout(pleaserefertotheinformationaboutthe2-bytetemperatureformatreadoutbyDS18B20)----------T_FORMAT:;AlarmsubroutineALARM:;DisplaysubroutineDISPLAY:;1MSdelay(calculatedby12MHZ)D1MS:MOVR7,#250llmm:nopnopDJNZR7,llmmRET;1MSdelay(calculatedby12MHZ)D1S:MovR6,#4LOOP2:movR5,#125;------------250LOOP1:LCALLD1mSDJNZR5,LOOP1DJNZR6,LOOP2RET;7-segmentdigitaltube0-9digitcommonanodedisplaycodeNUMTAB:DB0C0H,0f9H,0a4H,0b0H,99H,92H,82H,0f8H,80H,90H,0ffHXIAOSHU:DB00H,01H,01H,02H,03H,03H,04H,04H,05H,06H,06H,07H,08H,08H,09H,09HENDVIApplicationinAgriculturalProductionThistemperaturemeasurementsystemcandirectlyoutputdigitalquantities.Inaddition,ithasthecharacteristicsofsimplestructure,convenientuseandlowprice.Therefore,itcanbewidelyusedinagriculturalproduction.6.1TemperatureofMildewModerngrainwarehousescanusethissystemtomonitorthetemperatureofhundredsofpoints.Inthisway,youcaneasilygraspthetemperaturechangesatvariouspointsatdifferenttimes,increasestoragecapacity,andeffectivelyreducetheoccurrenceofmildew.6.2TemperatureofAgriculturalProductsAtpresent,low-temperaturerefrigerationmeasuresarewidelyadoptedforthepreservationoffruitsandvegetables.Thesystemcanbeinstalledinthetemperaturemeasurementpositionoftherefrigeratorcompartment.Inthisway,thetemperaturevaluecanbeconvenientlyobservedatanytimetocheckwhethertheoptimalpreservationtemperatureisreached.6.3TemperatureDetectioninGreenhousesThesystemisusedinplasticgreenhousesforgreenhousevegetablecultivationandflowerproduction.Inthisway,automatictemperaturedisplaycanberealized,andlaborandtimefortemperaturemeasurementcanbesaved.6.4TemperatureofSoilIntheprocessofplantingcropswithstrictrequirementsonsoiltemperature,thesystemcantestthechangesinsoiltemperatureasneededtofacilitatethegraspofaccuratetemperaturevalues.VIIConclusionThesingle-chiptemperaturemeasurementsystemtakesfulladvantageofthesimplicityofthehardwarestructureofDS18B20andAT89S52,using8-segmentdigitaltubedisplay,lowpriceandwideapplication.Accordingtoactualneeds,wecanalsouseLCDasadisplaydeviceorformadistributedtemperaturemeasurementandcontrolsystem.Althoughthedesigniseasytoexpand,italsohasitsshortcomings.Thesimplicityofthehardwarestructurecomesattheexpenseofsoftware.Therefore,specialattentionshouldbepaidtotheworkingsequencerequirementsofDS18B20duringprogramming.Inshort,thesystemcanbewidelyusedintemperaturemeasurementinagriculturalproduction.FAQWhatisDS18B20temperaturesensor?TheDS18B20isa1-wireprogrammabletemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.HowdoestheDS18B20work?Itworksontheprincipleofdirectconversionoftemperatureintoadigitalvalue.IsDS18B20athermistor?Athermistorisathermalresistor-aresistorthatchangesitsresistancewithtemperature....Thermistorshavesomebenefitsoverotherkindsoftemperaturesensorssuchasanalogoutputchips(LM35/TMP36)ordigitaltemperaturesensorchips(DS18B20)orthermocouples.HowaccurateisDS18B20?TheDS18B20readswithanaccuracyof0.5Cfrom-10Cto+85Cand2Caccuracyfrom-55Cto+125C.Whatisds1820?TheDS18B20isonetypeoftemperaturesensoranditsupplies9-bitto12-bitreadingsoftemperature....Thecommunicationofthissensorcanbedonethroughaone-wirebusprotocolwhichusesonedatalinetocommunicatewithaninnermicroprocessor.HowdoIconnectmyDS18B20tomyRaspberryPi?OnceyouveconnectedtheDS18B20,powerupyourPiandlogin,thenfollowthesestepstoenabletheOne-Wireinterface:1.Atthecommandprompt,entersudonano/boot/config.txt,thenaddthistothebottomofthefile:2.dtoverlay=w1-gpio.3.ExitNano,andrebootthePiwithsudoreboot.WhatistheworkingprincipleofDS18B20?TheDS18B20DigitalThermometerprovides9to12-bit(configurable)temperaturereadingswhichindicatethetemperatureofthedevice.Itcommunicatesovera1-Wirebusthatbydefinitionrequiresonlyonedataline(andground)forcommunicationwithacentralmicroprocessor.Inadditionitcanderivepowerdirectlyfromthedataline(parasitepower),eliminatingtheneedforanexternalpowersupply.ThecorefunctionalityoftheDS18B20isitsdirect-to-digitaltemperaturesensor.Theresolutionofthetemperaturesensorisuser-configurableto9,10,11,or12bits,correspondingtoincrementsof0.5C,0.25C,0.125C,and0.0625C,respectively.Thedefaultresolutionatpower-upis12-bit.WheretouseDS18B20Sensor?TheDS18B20isa1-wireprogrammableTemperaturesensorfrommaximintegrated.Itiswidelyusedtomeasuretemperatureinhardenvironmentslikeinchemicalsolutions,minesorsoiletc.Theconstrictionofthesensorisruggedandalsocanbepurchasedwithawaterproofoptionmakingthemountingprocesseasy.Itcanmeasureawiderangeoftemperaturefrom-55Cto+125withadecentaccuracyof5C.EachsensorhasauniqueaddressandrequiresonlyonepinoftheMCUtotransferdatasoitaverygoodchoiceformeasuringtemperatureatmultiplepointswithoutcompromisingmuchofyourdigitalpinsonthemicrocontroller.HowconnectDS18B20toArduino?FirstplugthesensoronthebreadboardtheconnectitspinstotheArduinousingthejumpersinthefollowingorder:pin1toGND;pin2toanydigitalpin(pin2inourcase);pin3to+5Vor+3.3V,attheendputthepull-upresistor.OnanATMega328P,whyisaDS18B20temperaturesensorreturningincorrecttemperaturevalues?Severalpossibilities:1.Ifitisjustreadingalittlehigh,itmightbecausedbyselfheating.Addaheatsinkand/ormakemeasurementslessfrequently.2.Especiallyifthevaluesarereallywhacky,itmightbecodewitherrorsormis-wiring.Useapublishedsketchtocheckoperation.3.TheDS18B20mightbedefective.Tryanother.4.Itsaccurateto0.5C.Areyouexpectingittobemoreaccurate(likedowntotheLSBofthereadvalue)?IDescriptionThisblogintroducesandanalyzes4simpleandeasy74LS00NandGatecircuitdiagrams.Itsincluding:SquareWaveGeneratorCircuit,PulseGeneratorCircuit,LEDLightCircuit.Andintheend,wewillanalyzethecircuitthatturnsthetimerintoacountdowntimerindetail.ThisVideoisAnIntroductionof7400LogicDevicesCatalogIDescriptionIISquareWaveGeneratorCircuitIIIPulseGeneratorCircuitIVLEDLightCircuitVTurnTimerintoCountdownTimer5.1SchemeDesign5.2ImplementationofSchemeDesignOrdering&QuantityIISquareWaveGeneratorCircuitLetstakealookatthefigurebelow.Itsasquarewavegeneratorcircuit.Thiscircuitcontainsa74LS00NandGateintegratedcircuit.Figure1.SquareWaveGeneratorCircuitDiagramAmongthiscircuitdiagram:NANDgates1,2andexternalRCtimeconstantcomponentsformanoscillatorcircuitNANDgate3isabufferoutputstage.AslongasthecapacityofCischanged,squarewaveoutputsofdifferentfrequenciescanbeobtained.IIIPulseGeneratorCircuitFigure2.PulseSignalGeneratorCircuitDiagramThecircuitdiagramisshowninFigure2anditsasimplepulsesignalgeneratorcircuit.ThesignalgeneratormainlyusestwoTTLintegratedcircuits(74LS00and74LS221).Sowhychoosethesetwocircuits?Thatisbecause,thesetwocircuitscanbeusedtogenerateapulsesignalof=4s.Besides,itusesfewercomponentsandisconvenientfordebuggingandmaintenance.IVLEDLightCircuitThiscircuitismadewithNE555,74LS00,74LS154,74LS193andLEDlights,andtheproductionprocessisverysimple.Whenweturnonthepower,hereishowitworksis:WhentheoutputQ0ofthe74LS154decoderislow,the74LS193isapositivecounter.Atthistime,theLEDsareindividuallylitfromD1...D16;WhentheoutputQ15ofthe74LS154decoderislow,the74LS193isacountdowncounter.Atthistime,theLEDsareindividuallylitfromD16...D1.Figure3.LEDLightCircuitDiagramFromtheabovewecanseethat:theLEDlightsturnonfromD1toD16,andthenbacktoD1fromD16,andsoon.VTurnTimerintoCountdownTimerGenerally,therearetwodesignideasforturningatimerintoacountdowntimer:First,changethecountingchipinthetimer;Second,resetthefunctionofthechip.Besides,thereisactuallyanotherwaytoachievethisgoal:Byappliyingthe74LS00and74LS20chipstoreversetheresultsonthedisplay,soastoachievethepurposeofcountingdown.5.1SchemeDesignTheresultdisplayedbyeachdigitofthetimerisanincrementalvalue,suchas0.1.2.3.4.5.6.7.8.9.Yet,thecountdowntimerdisplaysadecreasingvalue,suchas9.8.7.6.5.4.3.2.1.0.Aslongasthedisplayresultconversioniscompletedwithasuitablelogiccircuit,thetimercanbeturnedintoacountdowntimer.Atfirst,weneedtofindthelogicalrelationshipbetweenthetimerdisplayresultandthecountdowntimerdisplayresult.Table1belowliststheBCDcodescorrespondingtoeachdisplayresultofthetimerandcountdowntimer.Fromthistable,youcaneasilyfindtheBCDcodesofthetimerandcountdowntimer:ThelowestbitQ1andY1areopposite;WhileQ2andY2arethesame;RelationshipbetweenQ3andY3:Y3ofthecountdowntimeristheexclusiveORoftimerQ3andQ2;RelationshipbetweenQ4andY4:TheY4bitofthecountdowntimeristheoppositevalueoftheORofQ4,Q3,andQ2ofthetimer,whichisalsoequaltothenon-re-ANDofQ4,Q3,andQ2.Table1.CorrespondingBCDCodeDisplayedby(Down)TimerTheabovelogicalexpressionis:Therefore,aslongasyouchooseacircuitthatcancompletetheabovelogicconversionrelationship,youcanrealizethedesignfromatimertoacountdowntimer.Thefigure?showsatwo-digittimercircuit.Afteraddingtheaboveconversioncircuit,itbecomesthefigure3showsthecountdowncircuit.Figure4.TimerCircuitDisplaying2DigitsFigure5.CountdownCircuitDiagram5.2ImplementationofSchemeDesignTwokindsofchips74LS00and74LS20areuesdhere.Theformerarefourtwo-inputNANDgates,whichareusedtocompletetheconversionofY1andgeneratethenegationofQ4,Q3,andQ2.Thelatteraretwofour-inputNANDgates,whichareusedtoobtainY4fromthenon-reANDofQ4,Q3,andQ2.Insummary,wecanfollowthelogicalrelationshipasfollows:ThelogicdiagramisshowninFigure6.Figure6.LogicDiagramKnowingthattheXORgateoperationcanbecompleted,theY3conversioncanbecompleted.Theconnectioncircuitdiagramoftheabove-mentionedY4,Y3,Y1conversionspecificphysicalobjectsisshowninFigure7.Figure7.Y4,Y3,Y1ConversionSpecificPhysicalConnectionDiagramFigure8showstheactualpictureofthecountdowntimer.Figure8.CountdownTimerSofar,thetimerhasbecomeacountdowntimer.Throughthisdesignmethod,thereisnoneedtochangetheoriginalcountercircuit,isitparticularlytrouble-free?

I.IntroductionTDA7294isaveryinnovativeDMOShigh-powerintegratedamplifiercircuitlaunchedbythefamousEuropeanSGS-THOMSONSTMicroelectronicstomainlandChinainthe1990s.Itsweepsawaytheraw,cold,andhardtonesofthepreviouslinearintegratedpoweramplifiersandthickfilmintegration,andiswidelyusedintheHI-FIfield:suchashometheater,activespeakers,etc.Thedesignofthischipfocusesontone,andhastheadvantagesofbipolarsignalprocessingcircuitandpowerMOS.Ithasthecharacteristicsofhighvoltageresistance,lownoise,lowdistortion,andveryaffinityforreplayingsound;andhasasilentstandbyfunction,short-circuitcurrentandoverheatprotectionfunctionstomakeitsperformancemoreperfect.ThisarticlewillintroduceseveralpoweramplifiercircuitdesignsbasedonTDA7294.CatalogI.IntroductionII.OCLCircuitIII.BTLCircuitIV.ConstantCurrentPowerAmplifierV.Hi-FiIntegratedPowerAmplifierVI.ActiveSubwooferAmplifierAddsStandbyFunctionVII.HighFidelityPowerAmplifierVIII.ClassABPowerAmplifierIX.Two-channelPowerAmplifierX.100WPowerAmplifierCircuitOrdering&QuantityII.OCLCircuitTheOCLcircuitdiagramisshowninFigure1.Thiscircuitisadual-channel70WpoweramplifiercomposedoftwoTDA7294.Therearefewexternalcomponentsandsimplecircuit.Whenthepowersupplyvoltageis35V,70Wcontinuousoutputpowercanbeobtainedonan8ohmload.Itisverysuitableforplaybackinanenvironmentbelow30squaremeters.Ifthespeakerimpedanceislessthan8ohms,thepowersupplyvoltageshouldbereducedaccordingly.Figure1OCLCircuitDiagramIII.BTLCircuitTheBTLcircuitisshowninFigure2.ItusestwoTDA7294bridgestoformaBTLpoweramplifiercircuit.Theoutputpowercanreachmorethan150W.Itissuitableforplacesthatrequirehighpowersuchasdancehalls.4TDA7294arerequiredforstereo.Whenthepowersupplyvoltageis25V,acontinuousoutputpowerof150Wcanbeobtainedonan8ohmload.Whenthepowersupplyis35V,acontinuousoutputpowerof180Wcanbeobtainedona16ohmload.WhenuseTDA7294asBTLpoweramplifier,theloadmustnotbelessthan8ohms.Figure2BTLCircuitDiagramIV.ConstantCurrentPowerAmplifierThispoweramplifiercircuitissomewhatdifferentfromtheprevioustwostructures.Itsfeedbackcircuitiscurrentsampling,voltagesummationandnegativefeedback.Thiskindofcircuitstructureistheconstantcurrentpoweramplifierthatpeopleoftensay.Thespecificanalysisofthecircuitwillnotbedetailed,onlythemoreprominentadvantagescomparedwiththetraditionalconstantvoltagepoweramplifierwillbeintroduced.(1)Theoutputcurrentofthepoweramplifierhasnothingtodowiththeloadimpedance.Eveniftheloadisshort-circuited,itwillnotcausetheamplifiertooverheat.(2)Theoutputpowerincreaseswiththeincreaseofloadimpedance.Pushingthespeakerloadwithinacertainpowerreservecanensurethebassstrengthandhighfrequencyresolutionoftheoriginalmusicsignal.(3)Theforceactingonthevoicecoilofthespeakeronlydependsonthecurrent.Theuseoffluid-controlledoscillationtopromotethespeakermustbefasterthanthevoltage-controlledoscillation,sothattheinputandoutputimpedanceofthespeakervibrationsystemcanbeeasilymatched.Theconstantcurrentpoweramplifiercircuitisactuallyacontrolledcurrentsourcecontrolledbytheinputsignalvoltage.Itsinternalfeedbackcircuitiscurrentsampling,voltagesummingnegativefeedback,andithasthecharacteristicsofhighinputandoutputimpedance.Theinputimpedanceishigh,whichisexactlywhatthepreviousstageconstantvoltageamplifiercircuitneeds,whichisbeneficialforthesignalvoltagetobesenttotheinputendofthepoweramplifierwithoutloss.Thehighoutputimpedancecanreducetheshuntoftheinternalresistancetothesignal,whichisconducivetoaddingtheoutputsignalcurrenttotheload.InFigure3,thepowersupplyvoltageisselectedas35V,anditsmagnificationisdeterminedbytheratioofthespeakertoR6.Figure3ConstantcurrentpoweramplifiercircuitdiagramV.Hi-FiIntegratedPowerAmplifierThefamousEuropeanSGS-THOMSONSTMicroelectronicshaslaunchedaHi-Fihigh-powerDMOSintegratedamplifiercircuitTDA7294.ThecircuitisshowninFigure4.Itintegratesthebestdesignofmodernpoweramplifiercircuit,combinestheadvantagesofbipolarsignalprocessingcircuitandpowerMOS,hasthecharacteristicsoflownoiseandlowdistortion;standbyandmutecircuitcompletelyeliminatestheimpactnoisecausedbypoweronandoff,andeliminatesspeakerprotectioncircuitoverheating,short-circuitcurrentprotectionandotherfunctionsmakeitsperformancemoreexcellent.ThisdeviceissuitableforhometheaterandHi-Fiamplifiers.Themainparametersare:VS(powersupplyvoltage)10~40V(maximumvoltagewithoutsignal50V);Io(peakoutputcurrent)10A;Po(RMScontinuousoutputpower)70Wwhenvs=35V8;vs=70Wwhen27V4;(effectivevalueofmusicoutputpower)100WwhenVS=38V8;100WwhenVS=29V4.Figure4Hi-FiIntegratedPowerAmplifierCircuitDiagramTheclosed-loopgainofthecircuitinFigure4is30dB.IncreasingR3canincreasethegain,andviceversa,buttheamplifiergainshouldbe24dB.TheamplifierhasthebestperformancewhenR1=R3.R7,C4andR5+R6,C3determinethestandbyandmutetimeconstants.Thelargerthevalue,thelongerthetime.Whenthecontrolterminalisconnectedtolowpotentialground,itismuteandstandby;whenthecontrolterminalisconnectedtoVS,because(R5+R6)R7,pin⑩risestoahigherpotentialthanpin⑨,andturnstoalowpotentialfirstwhenshuttingdown,whichmakesthestandbyandshutdownprocessesgooninasilentstate,ensuringthattheamplifieristurnedonandoffwithoutnoise.Figure5BTLPoweramplifierfinishedboardForhigh-powerprofessionalapplicationsfiledssuchasdancehalls,youcanchoosetheBTLpoweramplifierfinishedboardshowninFigure5.BothTDA7294areequippedwiththeirownprofessionalradiators.Whenvs=25V8,themaximumcontinuousoutputpowerreaches150W;when35V16,Themaximumcontinuousoutputpowerreaches170W.WeusedTDA7294standardapplicationcircuitandMarantzPM80andYAMAHAA-592tomakealisteningcomparison.Theformerisamid-pricedHi-FimachinewithaClassA,ClassAandBstatusswitch,andthelatterisa439.16dollarsclasswithAc-3inputAVpoweramplifier,audiosourceismusicfaxE60CD,speakerisTannerNo.5.ItturnsoutthatthesoundorientationofTDA7294hasadistinctiveEuropeanstyle,soft,mellow,delicate,andfullofbouncingfeeling.ItissimilartotheMarantzPM-80inClassAandBstatus,butthesoundfieldofPM-80isdeeperwhenworkinginpureClassA.ComparedwithYAMAHAA-592,thedifferenceislarger.ThelowfrequencyofA-592seemstobeslightlyimproved.Itsoundspowerful,butitisharderandthelinesareblurry.TDA7294issweetandnatural,withhigherresolution,reallylikelandscapepaintingdonewithsplashesofinkandfine-brushflowersandbirds(atechniqueofchineseink-painting),eachhasitsinfinitecharm.VI.ActiveSubwooferAmplifierAddsStandbyFunctionThiscircuitisanimprovementontheaudiocircuitusingtheintegratedcircuitTDA7294.ThecircuitdiagramisshowninFigure6.TDA729410pinhasamutefunction.WhentheexternalDCprovideshighlevel,theintegratedblockisintheworkingstate;whenthelowlevelisapplied,theintegratedblockisinthecut-offstate.Atthistime,thecircuitconsumeslittlepowerandIC114pinhasnooutput,thatis,standbyform.Thegeneralcircuitistoprovideahighleveltopin10tomakeitintheconductingstate,infact,thedevelopmentofthispinfunctioncanmeetsomespecialworkrequirements.Thiscircuitisbasedonthistoincreasethestandbyfunctionoftheactivesubwooferpoweramplifier,anditscircuitisreliableandresponsive.Figure6ActivesubwooferamplifieraddsstandbyfunctioncircuitdiagramVII.HighFidelityPowerAmplifierThecircuitisshowninFigure7.ThedrivestageadoptsTDA7294.Theinternaldrivestageandoutputstageofthechipusefieldeffecttubes,whicharepoweredby40V,andtheoutputpowercanreach70W(RL=8;THD=0.005%).Ithasadelicatetoneandanexcellentsenseofhearing.PoweroutputVT1,VT2adoptsShankenhigh-powerpairtube2SA1394,2SC3858.Thecircuitprincipleisasfollows:ThesignalisinputtotheTDA7294non-invertinginputpin③throughC1andR1.R7andR3,C3,C4ofICpin②formanegativefeedbacknetwork,theclosedloopgainofthisamplifierisabout34times.The⑨and⑩pinsarethestandbyandmuteterminalsrespectively.SincetheRCnetworktimeconstantofthe⑩pinislargerthanthatofthe⑨pin,theswitchingmachinesareallperformedundermutesatge,avoidingtheswitchingimpactsound,andC7isabootstrapcapacitor.Figure7High-fidelitypoweramplifierpromotedbyTDA7294Productionpoints:(1)InsulatingmicasheetsshouldbeaddedbetweenthemetalcapandtheheatsinkofTDA7294(themetalcapisconnectedtothepin⑧).(2)Thepowertransformerusesring-shaped300Wdouble20V,four50V/10000Ffiltercapacitors,two50V/100F,andtwo100V/0.1F.Thepowersupplypartshouldbetestedseparately,firstwithoutconnectingthepoweramplifier,measurewhetherthepositiveandnegativeoutputvoltageofthepowersupplyaresymmetrical,theerrorshouldbewithin0.6V.(3)Whentestingthemachine,forsafetyreasons,youshouldfirstusealowervoltagetest(suchas25V)withoutaddingasignal,andmeasuretheDCvoltageoftheoutputterminaltotheground.Normally,itshouldbewithin20mV.(4)R8,R9,R10,D1formthefinalbiascircuit.ThisbiasmakestheoutputtubesVT1andVT2notcutoffduringoperation,sothequiescentcurrentcanbesmall(about5mA).(5)Thepowertubeshouldbestrictlymatched(within3%)andgenuineproductsshouldbeselected.TheoutputresistanceR14isa5Wnon-inductivetype,andtheinductorLisformedbytightlywinding10turnsonR14withadiameterof1.5mmenameledwire.TDA7294uses60mmTimes,85mmTimes,20mm12-slotheatsink,andtheoutputpairtubeneedsaprofessionalheatsink.Thesectionswithhighcurrentontheprintedboardneedtobetin-rolled,whichisextremelybeneficialforthetransparencyandstrengthofthesound.Figure8PoweramplifierPCBpromotedbyTDA7294VIII.ClassABPowerAmplifierTDA7294integratedcircuitcanbeusedasahigh-fidelityaudioclassABpoweramplifier.Itcandrive4ohmor8ohmspeakers,andwhenconnectedtoan8ohmspeaker,itwillprovide50wattsofoutputpowerand0.1%THD.Figure9ClassABpoweramplifiercircuitdiagramYoumustinstallalargeenoughradiatorforTDA7294.Pin10isamuteinput,andpin9providesastandbymode.Muteshouldalwaysoccurwhenselectingstandbymode.TheIChasinternalthermalprotection,whichcausesmutereductionat145C,andtheamplifierentersstandbyat150C.TheTDA7294integratedcircuitheatsinkisinternallyconnectedtothenegativepowerrail.Ifthemoduleisinstalledinagroundedmetalenclosure,thentheICmustbeinsulatedfromtheheatsink.Ifnot,thenegativepowerrailwillbeshortedtoground.IX.Two-channelPowerAmplifierTDA7294high-powerintegratedcircuitICisspeciallydesignedforassemblinghigh-performanceaudioamplifiers.TwoTDA7294piecescanbeusedtomakeapowerfuldual-channelhigh-fidelitypoweramplifier.ThecircuitprincipleisshowninFigure10.TheoverallcircuitiscomposedoftwoTDA7294corecomponents,andtheperipheryincludessomeresistorsandcapacitors.Thecircuitsofthetwochannelsarealmostidenticalindesign.TheyallusethestandardcircuitofficiallyreleasedbyTDA7294,connectedtoanon-invertingamplifiercircuit,withavoltagegainof30.5dB,anoutputpowerofupto70Wperchannel,andadualpowersupplysymmetricalpowersupplyvoltage35V.Amongthem,Cl5andCl6areinputcouplingcapacitors.0.47Fisusedintheoriginalcircuit.Here,ifyouincreaseitto1F,youcanimprovethelow-frequencyresponseofthecircuit.Itisrecommendedtousepolypropylenespecialaudiocapacitors,suchasWIMAsMKT4seriescapacitors,itcangreatlyimprovethesoundresolution.R3andR4areinputresistances,whichdeterminetheinputimpedanceofTDA7294inthein-phaseamplificationstate.Here,22kisrelativelymoderate.Toolargeavaluecanreducetheburdenonthefront-endsignalsource,butitmayaffectthestabilityofTDA7294andmaketheoutputmidpointvoltagedriftincreased,toosmallvaluewillaffecttheresponseabilitytolowfrequency.ThetheoreticalvalueofthefeedbackresistorsR7andR8shouldbeequaltotheinputresistorsR3andR4,whichcanensurethebiascurrentbalanceoftheTDA7294inputdifferentialcircuitandreducesignaldistortion.ThefeedbackgroundresistanceR5,R6cooperateswithR7,R8tosetthecircuitgain.Here,thefeedbackDCblockingcapacitorsCl3andCl4areusedtoformACnegativefeedback,inhibitDCvoltageoutput,andprotectthespeaker.Figure10Two-channelpoweramplifiercircuitdiagramTDA7294hasastartmutefunction,andcooperateswithanexternalcircuittoachieveanon-impactsoundeffectwhenthepoweristurnedonandoff.R9,R1O,R11,Rl2,Cl7,Cl8andVD5,VD6intheschematicdiagramformanexternalmutecontrolcircuit.Delaytheenergizationofpins9and10ofTDA7294toachievethefunctionofsoftstart.Thepowersupplyrectifierfiltercircuitisalsoverysimple.Thefullbridgerectifiercircuitiscomposedof4EuropeanspeedrectifierdiodesVD1-VD4.CapacitorsC1andC2arethemainfiltercapacitors.Large-capacityandhigh-currentaudiofiltercapacitorsarerequired,suchasELNAsFORAUDIOseriesorBHCAerovoxindustrialgradecapacitors.DesignPCBisgenerallyabottleneckinamateurproduction,sothatmanyexcellentschematicdiagramshavenotbeentransformedintofinishedPCBsthatcanbeactuallyassembled.Here,thepopularProtel99sedesignsoftwareisusedtodrawtheprintedcircuitboardagainsttheschematicdiagram10,asshowninFigure11.The2mmthickFR-4board-baseddouble-sidedPCBisused,andthecopperfoilisthickenedto70mm,whichissuitableforhighcurrentpoweramplifiers.ThewholePCBtraceadoptsone-pointgroundingmethod,whicheffectivelyeliminatesgroundwireinterferencenoise.Insomehigh-currenttraces,tinplatingisalsoadoptedtoincreasetheadditionalcurrentcarryingcapacity.Thepowerinputandpoweroutputstructureuseshigh-currentscrewterminalstoensuresufficientover-currentcapabilityanddurabilityofrepeatedwiring.Figure11PrintedcircuitboardX.100WPowerAmplifierCircuitFigure12100WpoweramplifiercircuitdiagramcomposedofTDA7294Figure12isa100WpoweramplifiercomposedofamonolithicaudiopoweramplifierintegratedcircuitTDA7294.TDA7294includespre-opamplifier,finalpoweramplifier,temperatureprotection,shortcircuitprotection,mutecontrolandothercircuits.ThefinalstageadoptsbipolarDMOSpowertransistor,whichhasthecharacteristicsofhighoutputpower,bandwidth,lowdistortion,andgoodversatility.Theintegratedcircuitalsohasperfectanti-overload,anti-shortcircuitandtemperatureprotectioncircuitfunctions.Whenthechiptemperatureistoohigh,itautomaticallycutsofftheaudiosignaltoprotectthechipfromburningThepoweramplifiercircuitcomposedofTDA7294hasthecharacteristicsofsimpleperipheralcircuitandeasyproduction.Thecircuitinputimpedanceis20k,theinputsensitivityis750mV,thevoltagegainis32dB,thepowersupplyvoltagerangeis(25~40)V,andthequiescentcurrentis50mA.Whentheloadimpedanceis8,theoutputpoweris100W;whentheloadimpedanceis4,theoutputpowercanreach180W.Inactualproduction,TDA7294shouldbeequippedwithenoughheatsinks.Thesupportingpowercircuitshouldhavesufficientcapacity.Ifyouneedtoincreasethecircuitvoltagegain,youcanappropriatelychangetheratioofR3toR2,voltagegainA=201g(R3/R2)(dB).However,itisnotadvisabletoone-sidedlypursuethevoltagegainofthisstage.Excessivevoltagegaincaneasilycausecircuitself-excitation.Thesolutionistoincreasethevoltagegainofthepre-stage.I.DescriptionTDA2030Aisoneofthehigh-fidelityintegratedpoweramplifiers,andmanypoweramplifiercircuitsusethisintegrationmethod.TDA2030isalsoaHI-FIpoweramplifierintegratedblockusedbymanycomputeractivespeakers.Ithassimpleconnectionmethodandaffordableprice.Theratedpoweris14W.Thepowersupplyvoltageis6~18V.Theoutputcurrentislarge,theharmonicdistortionandthecrossoverdistortionaresmall(14V/4ohm,THD=0.5%).Ithasexcellentshortcircuitandoverheatprotectioncircuit.Thefollowingdescribesitsconnectionandapplicationcircuit.CatalogI.DescriptionII.Connection2.1SinglePowerConnection2.2DualPowerConnectionIII.ApplicationCircuit3.1OTLFormPowerAmplifier3.2OCLFormPowerAmplifier3.3BTLFormPowerAmplifier3.440WPowerAmplifierCircuit3.5High-fidelityActiveSpeakerCircuit3.625WBridgeLowFrequencyPowerAmplifierCircuitOrdering&QuantityII.ConnectionItsconnectionmethodisdividedintosinglepowersupplyanddualpowersupply:2.1SinglePowerConnectionFigure1TDA2030singlepowerconnectiondiagram2.2DualPowerConnectionFigure2TDA2030dualpowerconnectiondiagramIII.ApplicationCircuit3.1OTLFormPowerAmplifierOTLformpoweramplifier:singlepowersupply,outputcouplingcapacitor.TheR5(150k)andR4(4.7k)resistorsinthecircuitshowninFigure3determinetheclosed-loopgainoftheamplifier.ThesmallertheR4resistor,thegreaterthegain,buttoolargegaincaneasilycausesignaldistortion.Twodiodesareconnectedbetweenthepowersupplyandtheoutputterminaltopreventtheinductiveloadofthespeakerfromkickingbackandaffectingthesoundquality.ThecapacitorofC3(0.22uF)andtheresistanceofR6(1)areusedtocompensatetheinductiveload(speaker)toeliminateself-excitation.Thecircuitusesa36Vsinglepowersupplyandtheoutputpowerisabout20W.Figure3OTLtypepoweramplifiermadewithTDA2030A3.2OCLFormPowerAmplifierTheformoftheOCLpoweramplifieradoptsdualpowersuppliesandhasnooutputcouplingcapacitor.AsshowninFigure4,sincethelowfrequencyresponseoftheoutputcouplingcapacitorisimproved,itisahigh-fidelitycircuit.Thedualpowersupplyusesatransformerwiththemiddlepointoftheprimarycoilgroundedandtheupperandlowervoltagesaresymmetricalandequal.Afterrectificationandfiltering,a18Vdualpowersupplyisformed,andtheoutputpoweris20W.Figure4OCLtypepoweramplifiermadewithTDA20303.3.BTLFormPowerAmplifierThemainfeatureofBTLis:itiscomposedoftwoidenticalpoweramplifiers,andtheinputsignalsareinversetoeachother.Thein-phaseinputandtheinvertedinputoftheamplifierareactuallyusedtoensurethattheinputsignalsareinversetoeachother.Atthesametime,theamplitudesofthetwoinputsignalsshouldbethesame,sothatthebasicrequirementsoftheBTLcircuitformcanbemet.ThecircuitdiagramisshowninFigure5,whereR7(1k)andR8(33)resistorsdividethesignalandtheattenuationfactorisexactlythesameastheamplificationfactorofU1.TheattenuatedsignalisaddedtotheinvertinginputterminalofU2throughR5.Infact,twoopampscompleteasignalamplification,andtheactualmeasuredoutputlevelis1.5timeshigherthanthatofanintegratedcircuit.Thatis,theoriginaloutputpoweroftheopampis20W,andtheoutputpowerisnowabout50W.However,duetothecharacteristicsoftheBTLcircuit,whenchoosinganintegratedcircuit,usetwooperationalamplifiercircuitswiththesameparametersasmuchaspossibletoadjusttheinputsignalamplitude.Youcanuseanoscilloscopetoobservetheamplitudeofthetwoinputsignalsbyinputtingasinewave.Atthistime,adjustR7tomakethetwoinputsignalsTheamplitudeisthesametoensurethatthenonlinearsymmetrydistortionisminimizedwhileincreasingthepower.Figure5BTLtypepoweramplifiermadewithTDA2030A3.440WPowerAmplifierCircuitFigure6isa40WpoweramplifiercircuitmadebyTDA2030poweramplifierintegratedblockandBD907/908:Figure640WpoweramplifiercircuitmadebyTDA20303.5High-fidelityActiveSpeakerCircuitAhigh-fidelityactivespeakercircuitdesignedwithTDA2030,thecircuitdiagramisshowninFigure7.Usingdualpowersupply,addedhighandlowbassandvolumeadjustment.WhendesigningthePCB,thegroundwireshouldnotpassthroughthecomponentpinsasmuchaspossibletoreduceDCnoise.Figure7Highfidelityactivespeakercircuitdiagram3.625WBridgeLowFrequencyPowerAmplifierCircuitFigure825WbridgelowfrequencypoweramplifiercircuitThecircuitinFigure8usestwoTDA2030sconnectedtoformabridgecircuit,withthesamecircuitstructureandparametersonbothsides.Theintegratedcircuitontherightiscontrolledbytheintegratedcircuitontheleftthrougha22knegativefeedbackresistor,andviceversa.Thediode1N4001isusedtopreventthespeakerinductiveloadfromgeneratingovervoltageanddamagingthedevice.Theamplificationfactorofthecircuitcanbeadjustedbychangingthenegativefeedbackvoltageratiobetweentheoutputterminal(pin4)andtheinvertinginputterminal(pin2).