More Power to You
Posted date : Apr 6, 2006

Philips is building more and more high voltage/power products on SOI. Here’s why.

Since the 1990’s, Philips has been and continues to be a pioneer in SOI-based high-power and high-voltage ICs (handling anywhere from 12 to 800 volts).

Now these chips are everywhere. They’re in smaller, lighter power modules and battery-chargers for a whole host of products, including PC monitors and peripherals, TVs and set-top boxes, DVDs and CD players, consumer electronics, medical equipment and more.

Plus they’re found:

helping cars run safer and more comfortably,
• in smaller, lighter audio equipment that plays louder but stays cooler,
• and in high-power management systems and power converters that run smarter.

SOI Advantages

With SOI, all the components formed on the chip can be completely isolated. Citing its SOI-based A-BCD (advanced bipolar CMOS DMOS) process, Philips notes key advantages. First, when transistors are in the on-state, resistance is reduced by more than 20% (depending on the source and the applied voltage) compared to equivalent bulk. That means the chips can handle higher power levels and produce less waste heat.

Second, they’re intrinsically free from latchup (a situation that can occur in bulk silicon where transistors are overloaded and effectively become “stuck” in the on-position). With cross-talk, load dump and other accidental high external voltages virtually eliminated, robustness and reliability are greatly improved. Multiple power devices, bridge rectifiers and flyback diodes can be integrated on the same piece of silicon, as can CMOS, Bipolar, JFET and DMOS devices, enabling the creation of real Smart Power circuits.

Third, much greater packing densities – on the order of 20 to 30% smaller – can be achieved.

Fourth, parasitic capacitances are also significantly reduced, so it is much easier and quicker for designers to work with.

And finally, the chips have far greater heat tolerance, easily functioning up to 160°C compared with bulk silicon’s 125°C inside the chip. This means that high power handling ICs can be created without heat sinks, further reducing both size and costs. Plus, they can operate correctly in very hot environments (under the hood of a car, for example).

High voltage, low cost

Philips contends that while the cost of the SOI starting material is higher than bulk, this is compensated for by the lower number of mask steps. In Philips’ A-BCD1 process, for example, there are thirteen mask steps, which is three or four fewer than for an equivalent bulk silicon process. In addition, improved packing density, greater power handling and simplified designs result in the production of competitively-priced chips.

Consider the STARplug™, for example, a family of SOI-based power plug chips. They are a turn-key solution enabling product designers to respect the laws of “smaller, faster, cheaper, better” for audio/video, white goods, personal care, communications and networking, PC peripherals and more. The STARplug chip designs combine a low-voltage BiCMOS process with Philips’ EZ-HV™ SOI process in a thin layer of silicon. This keeps the costs low while enabling high and low voltage components to be placed in close proximity.

With all these advantages, it’s no surprise that Philips plans to base more and more new products on SOI technology.

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