Does SOI matter to the designers using the chips?

By Adele Hars
Much of the SOI vs. bulk discussion zeros right in on the manufacturing bottom line:  which is cheaper?   And absolutely, customers want the most cost-effective solution.  But the best of all possible worlds is if you can save them money and give them all the bells and whistles they’re looking for, too, right?

Guenter Reiniger, NXP Marketing Manager, Automotive Sensors

At ASN, I recently had a chance to talk to Guenter Reiniger, Marketing Manager for NXP’s Automotive Sensors.  Designers of automotive electronics are under enormous pressure these days to deliver more for less.  NXP sells to just about every carmaker on the planet, and their automotive chips have been on SOI for years.

In the following interview, Dr. Reiniger explains how SOI helps eliminate the need for external components in a new magnetic sensor family.  While this interview concerns a particular sensor family, the ramifications of choosing an SOI-based solution hold across a much broader range of chips and markets.

Advanced Substrate News (ASN): NXP recently announced the KMA210, the first in a new family of magnetoresistive (MR) sensor chips. What is it used for?

Guenter Reiniger (GR): The KMA210 is a position sensor for automotive applications wherein a precise mechanical angle needs to be measured. So on one hand you can use it in things like electronic steering, active suspension and automatic headlight adjustment. But because it’s very accurate and very robust, it’s also an excellent choice for under-the-hood applications such as power train, throttle control and air control valve measurements. And since it operates in temperature ranges up to 160°C, it’s ideal for things like emissions control and clean diesel applications.

ASN: The MR technology isn’t new – what’s new about this chip?

GR: MR technology was pioneered by Philips and a few others over 30 years ago, so it’s proven and robust. We’ve been selling MR sensors in very high volumes for many years – Continental alone has used over half a billion in its ABS systems. What’s new here is our ability to incorporate the signal-conditioning ASIC with the MR sensor in a full system-in-package solution. That’s where the SOI comes in.

ASN: Why did you need SOI?

GR: Our customers now have to meet extremely rigorous requirements, especially with respect to safety, emissions controls, electromagnetic compatibility (EMC) and electrostatic discharge (ESD). Previous solutions involved the sensor plus separate bulk-silicon-based components that our customers would incorporate on a board. To cost-effectively incorporate the sensor with the requisite electronics in a single package, we need to put the signal-conditioning ASIC on 140nm SOI using our latest ABCD9 process technology.

ASN: Why is that?

GR: SOI gives our chip designers a number of advantages, such as:

• Reduced resistance for the transistor in the on-state (R_ds(on)), so much less waste heat is produced, which we leveraged to make a much smaller chip.
• Much greater packing densities
• Latch-up-free behavior, since there are no parasitic junctions between N-type and P-type devices.
• Ability to handle voltage spikes from the starter motor or alternator
• Greatly improved heat tolerance.
• Easy integration of multiple power devices, bridge rectifiers, and flyback diodes on the same piece of silicon. In combination with a significant reduction in parasitic capacitance, this simplifies and speeds the chip design process.

ASN: In addition to the cost effectiveness for you, what advantages does SOI confer to your customer, the automotive designer?

GR: We created this product in very close partnership with our customers. By implementing the ASIC on ABCD9 SOI, the interface areas of the ASIC have 16V overvoltage protection – in bulk the chip would have been too big and too expensive. From the automotive designer’s perspective, they can use the same socket they used for previous generations when it was just the sensor – but now they don’t have to design a board to go with it – everything’s in there. The device contains two embedded block capacitors (for Vdd and output) within the same package. And of course you get the advantages you always get with SOI: robustness in terms of EMC, ESD and high temperatures. The package really reduces system cost: there’s no additional design, no boards, no external filter components, no lead frames. All told, the KMA210 position sensor with the integrated ASIC on SOI gives the automotive designer the key to a cheaper, smaller and more robust measurement solution.

An example of how NXP's KMA210 magneto-resistive sensor would be used in a throttle position application. Because the KMA210 is manufactured using NXP's ABCD9 process technology on SOI, the signal-conditioning ASIC and the sensor are fully integrated in a system-in-package solution that requires no additional external components. (Courtesy: NXP)

ASN: What does the future hold?

GR: With ABCD9 on SOI, we are working on a next generation of these chips for temperatures up to 200°C. For next year, we’ll also have a redundant version (with two devices in one package), and a version with digital output. While perhaps we could have done all this without ABCD9 and SOI, we couldn’t have done it under the same commercial conditions. These are really cost-effective devices.

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So, cost-effective devices on SOI make a huge difference both to the chip designer and to the car designer. Who could ask for anything more?

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