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V460LT10PX2855_Datasheet PDF

时间:2021-06-14 01:04:21 来源:网络整理编辑:Touchstone Semiconductor

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Citing preliminary results released earlier this year by Dataquest Inc., which showed worldwide semiconductor revenues growing 17.8 percent in 1999, Pistorio said, The market without DRAM grew 16 percent last year and we grew 19 percent. We believe ST is positioned to grow more than the market in 2000.”

Citing preliminary results released earlier this year by Dataquest Inc., which showed worldwide semiconductor revenues growing 17.8 percent in 1999, Pistorio said, The market without DRAM grew 16 percent last year and we grew 19 percent. We believe ST is positioned to grow more than the market in 2000.”

One group of manufacturers-National Semiconductor and Maxim Integrated Products, for instance-is concentrating on low-power products, like headphone amplifiers for cell phones and PDAs, in which the power saving of Class D is absolutely demanded, the filter requirement is minimal and any compromise in sound quality will largely be unnoticed. Another, so far very small, group, typified by manufacturers like D2Audio Corp. (Austin, Texas), is trying to offload the user of filter design problems altogether, by supplying only pretuned drop-in boards offering 120 W/channel (see Nov. 3, page 4). Up to eight channels are available on a 4.3 x 6.8-inch board. But with OEM modules selling for about $100 each, they will be used only by high-end consumer OEMs like Harman Kardan.

But the most visible group-typified by Tripath Technology, Texas Instruments and Apogee Technology (with parts made by STMicroelectronics)-is targeting the consumer mass market with high-power amplifier parts. These manufacturers are implementing zero-crossing,” spread-spectrum and other noise-reduction techniques in an effort to minimize the external filter requirement. (Cirrus Logic announced its intention to attack this portion of the market, although its Class D line so far has centered on a low-power headphone amplifier.)

V460LT10PX2855_Datasheet PDF

This camp of suppliers has argued, and occasionally demonstrated, that digital amplifiers can indeed approach audiophile quality. But they'll have their work cut out for them in getting digital amplifiers accepted by the golden ears” crowd.

In operation, digital amplifiers use the width and frequency of a digital pulse train-pulse-width modulation (PWM)-to carry an audio signal. The pulses are generated by trip comparators, matching the voltage levels of an audio signal against those of a sawtooth reference to trigger the pulses. Thus, a high-amplitude, high-frequency signal is represented by a dense cluster of short-duration pulses; a lower-frequency, lower-amplitude signal will have longer pulses, farther apart.

The audio signal is produced by pumping the digital pulse train into a pair of power MOSFETs, typically wired in a push-pull configuration. An additional inductor-capacitor filter (as well as the speaker coils themselves) adds persistence” to the signal, effectively smoothing out the pulses.

V460LT10PX2855_Datasheet PDF

Transistors are not natural amplifiers; they are switching devices. To get a transistor to behave as an amplifier, as with conventional Class AB amplifiers, you have to apply a bias current, which forces the transistor to forever hang in a region between being completely on and completely off. That means the transistors of the Class AB amplifier will be sucking up current-and generating heat-even when there is no audio signal present.

On top of that, audiophile equipment manufacturers have learned that many types of power transistors perform most linearly (and are claimed to sound the best) when they are hot biased”-that is, when they are given almost, but not quite, enough bias current to snap them into an on” state. This will make the power transistors extremely hot to the touch, and it is no wonder (or exaggeration) that these high-end Class A amplifiers will come with 30 pounds of aluminum heat sink.

V460LT10PX2855_Datasheet PDF

The digital amplifier, in contrast, uses power transistors much more efficiently. The pulse-width modulator switches them on or off and tries not to spend too much time (or power) in the in-between state. Consequently, the chain among PWM, driver stage and power transistor output in a Class D amplifier is significantly shorter than it is for multistage AB amplifiers.

The problem is that the output of the audio amplifier must be carefully filtered to block the residue and harmonics of the digital pulse train. That puts the semiconductor supplier in the filter design business, and there is no guarantee that the customer-the consumer electronics equipment maker-will adhere to the reference design or follow the semiconductor maker's recommendations. Thus, if the end consumer is unhappy with the sound quality of a home theater system, he or she might well blame the semiconductor supplier, when in fact it might be the fault of an underdesigned filter.

During the last half of 1999, ON Semiconductor added about 20 new ECL products, including devices that can handle 6 gigabits per second and operate at speeds of 170 picoseconds at 2.5 volts. These building-block ICs are faster than CMOS solutions and cost less than gallium-arsenide (GaAs) devices, Daniely said. The privately-held company is also considering other process technologies — such as silicon germanium (SiGe) — for future products in the high-bandwidth arena, he said.

ON Semiconductor emerged last August when a private investment group completed a $1.6 billion purchase of Motorola's commodity semiconductor division. The division had gathered an extensive ECL portfolio while still a part of Motorola's Semiconductor Product Sector, and since the spinoff, ON Semiconductor management identified a growth strategy for Internet and backbone technologies using the high-speed bipolar devices.

This market goes beyond the traditional ECL functions we have been selling,” Daniely said. We are now talking about components for the data path, such as high-speed multiplexing and demultiplexing, post amplifiers, op amps, laser drivers and other types of products for the data path and fiber optics.”

While pursuing new high-bandwidth ICs running at up to 40 gigabits per second, ON Semiconductor will continue to maintain its building-block focus in the marketplace. We are not looking at offering 'cores,' ” said Daniely, referring to reusable design blocks for system-level integration. We are not a system-on-a-chip company, but we are looking at doing higher levels of integration rather than just the primitive logic functions.”

TOKYO — As U.S. EDA vendors increase their presence in the Japanese market, one Japanese EDA company — Zuken Inc. — is heading in the other direction. Currently Japan's top provider of pc-board design tools, Zuken is launching a new effort to beef up revenue in Europe and North America, and to regain the No. 1 worldwide position it once held in pc-board design.