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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.
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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).
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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
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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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