MEMS devices absolutely blew my mind the first time I read about them. Thinking: "yeah, this just shouldn't exist". Like, how can you make something with moving parts out of something that normally doesn't move (polycrystalline silicon), and is very fragile at that, all the while doing it at a scale that you require similar processes as 'normal' semiconductors. You can make physical oscillators like the peeps do in this article and have surrounding circuitry to drive and measure them, levers and actuators to mount actual tools onto: probes to manipulate single cells, mirrors to control light (looking at you, DLP) and so many other things. Super interesting!
> out of something that normally doesn't move (polycrystalline silicon)
More commonly, bulk micromachined MEMS devices are monocrystalline.
> and is very fragile at that
Normalizing for density, monocrystalline silicon is stronger than steel!
Whoops, yep, thanks for the correction! What's a Greek prefix between friends (save for crystal properties).
One thing to realize about MEMS is that it is mostly used for sensors (accelerometers, gyros, pressure, magnetometers) and actuators. There's a whole journal by that name.
Fundamentally, an oscillator/resonator is the sensing of nothing.
You want the frequency of output to be completely independent of acceleration, strain, rotation, pressure, magnetic/electric field, etc). That's really hard to do and involves a combination of building very robust silicon packaging, minimizing (making symmetric) all contacts to the outside to shield it, and compensating for every possible effect you can measure.
Yeah, like all sensors, basically anything you make in MEMS is a temperature sensor, a pressure sensor, an acceleration sensor, and a strain gauge all in one. The trick is to make it only sense the thing you want.
FWIW I'm very impressed with the xMEMS tweeters in my earphones. I'd say they have the widest soundstage of any earphone i've ever listened to (even over lossy LC3). The MEMS mic on my qudelix 5k is also really good.
> Ian: There was a story a while ago with Tesla’s AI chip - they had to deliver power at a thousand amps per square centimetre.
Where can I read more about that?
> The beauty of using MEMS over quartz is multi-faceted.
That is crystal-clear to me.
Speaking from (independent) experience, the SiTime parts live up to the hype.
You do not want to be in the quartz crystal business going forward; it's almost as dead as vacuum tubes, even if the manufacturers don't know it yet. Nothing will be left to fight over but the very cheapest commodity parts.
It's pretty nuts - if you care at all about your frequency reference and have power or space constraints, SiTime seems to be beating everyone else right now.