Oops, meant to add -- your application sounds like a perfect
match for letting the PIC sleep most of the time and periodically=

waking it up to check for input triggers (if you have one?) or a=

timer based event.

If you use an external CMOS "wakeup circuit", you can probably
get your standby current down to well less than 100uA and run it=

directly from the battery voltage. I've used the CD4060 counter
and RC oscillator to periodically power up a PIC. You can use one=

of the counter outputs to enable a LDO regulator.

You should be able to stretch your battery life significantly
either way.

Matt Pobursky
Maximum Performance Systems

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