editor's blog
Subscribe Now

Comparing Oscillator Temp Compensation

MEMS oscillators are making a serious challenge to quartz these days. We looked at Sand 9’s approach recently, but as I thumbed back through other recent announcements, I came back across one that, in retrospect, had some relevant bits to discuss.

Silicon Labs’ earlier announcement focused on the CMOS+MEMS aspect of their work. At the time, I didn’t see anything I could add to the discussion, so I let the announcement stand on its own. But in light of some of the issues I covered in Sand 9’s release, I thought there were some things to come back to on the Silicon Labs story – some of which weren’t immediately apparent in their release.

This relates to temperature compensation, which seems to be the number one concern with these devices. Yes, everyone tries to compensate with circuitry, but if you can minimize the raw temperature effects, then the compensation is easier.

We looked at the stack that Sand 9 built to do this – silicon and oxide having opposing temperature coefficients and therefore physically compensating for each other. Well, Silicon Labs does something similar but not identical.

They use SiGe as the active material for the resonator, but they back it with SiO2, which again opposes the temperature characteristics of the SiGe.

The other subtlety here relates to the CMOS processing aspect, although again, it seems to be two different ways of accomplishing the same thing. Sand 9 discussed how having the compensation ASIC in the same package was important so that the ASIC was experiencing the same temperature as the sensor it was compensating.

With the Silicon Labs approach, this happens as a direct result of combining MEMS and CMOS on the same die: The compensation circuitry isn’t just next to the sensor; it’s on the same die as the sensor. So again, it experiences the same temperatures as the sensor. It’s probably even closer, although at some point, if you start arguing about hot spots on the actual die, you could question whether mere monolithic integration guarantees better compensation. It depends on where things are on the die and how “hot” the circuits are. So it remains to be proven whether monolithic compensation is practically any more effective than a well-engineered die-by-die solution.

You can find more on Silicon Labs’ process here.

Leave a Reply

featured blogs
Dec 14, 2018
Yesterday I wrote a sort of overview of the Cadence Automotive Summit that took place in November, in the post Automotive Summit: The Road to an Autonomous Future . Today, the focus in on a key part... [[ Click on the title to access the full blog on the Cadence Community si...
Dec 13, 2018
In November, we continued our mobile updates to the website, released a couple of new content experiences, and made placing sample requests even easier. Read more below on these and the rest of the major updates to Samtec.com for November 2018. Continued Improvements to our M...
Dec 10, 2018
With Apple'€™s '€œWearable'€ category of sales setting a new record this September with growth over 50%, and FitBit seeing growth in both trackers......
Nov 14, 2018
  People of a certain age, who mindfully lived through the early microcomputer revolution during the first half of the 1970s, know about Bill Godbout. He was that guy who sent out crudely photocopied parts catalogs for all kinds of electronic components, sold from a Quon...