There was more MEMS news today, this time from Kionix, a Cornell spin-off that positions itself among the top 3 providers of accelerometers, along with ST and Bosch.
They announced, among other things, a new accelerator/gyro combo – their first – and a new accelerometer sense element.
Combos aren’t new; we’ve discussed the fact that some integration is monolithic, but not in this case. They use separate chips. Of course, than means that alignment is critical when packaging them together; it’s what they refer to as “bias” (which has nothing to do, in this case, with a voltage). They handle this at three levels: when actually assembling (getting as close to aligned as possible) as well as through compensation both in the accompanying ASIC and in the “fusion software” that they’ve also just announced.
The CMOS ASIC is also on a separate die; they have no specific plans at present to integrate them onto a single chip. They believe that “bringing MEMS and CMOS processes together – remain[s] daunting, particularly when trying to achieve high yields.” They say they can achieve better costs by using separate dice.
Notably, they didn’t include a magnetometer in the combo. They point out that many OEMs are very picky about where the magnetometer should be placed in the system to minimize stray magnetic effects, so it’s likely to be positioned away from the other inertial measurement units (IMUs). Even though they don’t package them together, their fusion software does support magnetometers in the mix.
Interestingly, they say that gyroscopes haven’t really found their killer app yet (as compared to accelerometers, with their massive airbag market). Gyros also pose power problems: accelerometers are passive, but gyros need a vibrating mass to detect angular changes. Keeping the mass in motion takes power, and, typically, the controlling software will power the gyro up and down to conserve power.
As to their new XAC accelerator sense element, they’re being coy about what that is. According to their VP of Engineering, Scott Miller, “I can say that we took a hard look at weaknesses in previous sensor designs. We dropped parts hundreds of times. We ran parts through multiple solder reflow cycles. We wanted to understand what the sources were for any failures or shifts in performance. Once we knew that, we attacked them by making structural design changes, material changes, and process changes. The result of this effort is the new XAC sense element.”