The AA Power board announced yesterday just arrived:
And it looks like it does indeed perform exactly as expected. Here’s the ripple:
That’s with the 1.6 mA LED load, i.e. a 75 µs cycle / roughly 13 KHz – this was as predicted: at light loads, the recharge frequency can reach down into the audible range. But it’s highly unlikely to be noticable due to the tiny size of the inductor, which after all is not built to act as a loudspeaker :)
Here’s the “AAv1” fully mounted for powering a JeeNode via the FTDI connector:
(there’s no charge circuit here, I’m just using an externaly-recharged battery as power source)
And here’s the whole setup in actual use:
Works like a charm. Runs just fine with the “rooms” and “radioBlip” sketches, and wireless just works – as before.
Quiescent current draw is about 20 µA when powered this way. That goes down to 10 µA when used with two cells @ 2.4V, and down to an amazing 7 µA when powered from a 3V source (a CR2032 ought to work nicely!). Above 3.3V, the circuit becomes just a tad less efficient when it switches into step-down mode, drawing about 30 µA all the way up to 5.5V.
Great, now we’re starting to get into some serious low-power options.
Tomorrow, I’ll describe other ways to use this new AA Power board…