Application Specific MOSFETs Modernize Airbag Design

Ally Winning, European Editor, PSD


Nexperia's new ASFET range brings advanced technology and small packaging to airbags

Application specific ICs have been an important part of electronics for at least a few decades at this point. They are intended to provide the features necessary to implement the main components of a design at a low price point and known power budget for manufacturers who either don’t have the engineering talent in-house to design a bespoke IC, who need to hit the market quickly to ensure they hit the sweet spot for sales, or may not be producing the device in large enough numbers to justify a unique design. Whatever the reason, ASICs eliminate a good part of the non-recurring engineering part of a design, as well as cutting down on design time. It is a system that has worked well, especially in times like these when engineers are scarce and semiconductor foundries have massive waiting lists.

Over the last year or two, Nexperia have taken the idea behind the ASIC and applied it to MOSFETs. The majority of applications can use any general MOSFET that has the correct figure of merit, but other applications have requirements for MOSFETs that general purpose devices can’t meet. In the last few years, Nexperia has targeted those markets by developing ranges of MOSFETs for specific applications. Since that strategy has started, Nexperia has developed bespoke MOSFET solutions for battery isolation, motor control, hot-swap, and Power-over-Ethernet (PoE) applications.. Now, the company has used the PCIM exhibition to launch the latest range of ASFETs, which target automotive airbag applications.

In airbag designs, current is passed through a detonator wire, which ignites a chemical explosive in the squib. That explosive releases a massive amount of gas as it burns, which fills the bag. To do the job properly, the energy has to build up in the detonator wire detonator, meaning it has to be supplied with current over a period of time. To accomplish this, the MOSFET has to have a large safe operating area (SOA). Unfortunately, the SOA is one of the metrics that has been left behind when manufacturers are making design choices. As a result, automotive designers being forced to use older MOSFETs in airbag designs, which do the job sufficiently, but miss out on taking advantage of most of the advances made in semiconductor design over the last decade. The new range of ASFETs are targeted mainly at the medium to low end vehicles that are made in large numbers. At the same time, the number of airbags has risen to 10 in some types of vehicle, so the potential market is massive.

The new range of ASFETs for automobile airbag applications are headlined by the BUK9M20-60EL single N-channel 60 V, 13 mOhm logic level MOSFET. BUK9M20-60EL uses Nexperia’s enhanced SOA technology to provide exceptional transient linear mode performance. It comes in an LFPAK33 package which uses 84% less board space compared to older DPAK packaging.

“Other similar products use older DPAK packaging and are typically based on DMOS and first-generation trench technologies which are being gradually retired by many silicon manufacturers,” said Norman Stapelberg, Senior Product Marketing Manager at Nexperia. “The ASFETs use a combination of the latest silicon trench technology and LFPAK packaging o allow it to meet the most recent reliability standards. Using the latest manufacturing and packaging technologies also makes the supply chain more sustainable.”