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On Fri, 25 Nov 2011 07:06:57 -0800 (PST), wrote:

On Nov 25, 12:46*am, Jeff Liebermann wrote:
On Thu, 24 Nov 2011 18:13:15 -0800 (PST),
wrote:

I found this, which calculates and measures caliper battery life:
http://www.davehylands.com/Machinist/Caliper-Batteries/

Yes, good site. I linked to it earlier in this thread.

Small, cheap and simple are the main factors here. *The r.c.m. guys
aren't going to be building switching regulators, and switching
regulators generally aren't more efficient at these power levels
anyhow--their quiescent current draw's too high.

True. *However, switching regulators usually have some manner of load
shedding when the supply voltage is insufficient. *Below that
threshold, the current drain is usually in nanoamps.

(I've made a study of designing microwatt switchers, from scratch.
It's possible, but wholly inappropriate here.)

You're ahead of me. *I've never designed anything in that low power
class. *Different world. *Can you point me to a suitable (or close to
suitable) regulator chip?

There aren't any ICs with low enough Iq, at least not that I know of.
I used discrete transistors.

There are some pretty good ones, designed for USB applications, but I don't
thing they're quite good enough for this. The TPS6205x Iq is around 5uA to and
in shutdown less than 2uA. You're looking for something an order of magnitude
better than this?

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