I've done a bunch of "blinkenlights" -type projects, but my current
thing will need to be more polished and user-friendly.  It's a small,
low-draw, battery-powered, output-mostly device.  I think it shouldn't
have a power button; it really needs to be either "on," or "off because
it needs to be recharged."  So I'm trying to figure out how to implement
this (other than just direct-wire the battery and let the device run the
battery completely flat.)

I'm thinking about a low-side FET with a gate pull-down to control the
microcontroller ground connection.  Connecting to the charger will pull
the gate up and turn on the uC, then the uC will keep its own power
turned on until it sees the battery get too low.  Then, it'll turn
itself off by discharging the gate, and it'll stay off until connected
to the charger again.

This seems a little dodgy to me, though, so I ask you professional
consumer-electronics people: what's a cheap, reliable way to turn the
power to a device on and off under the device's own control, without
requiring user interaction or a switch?

Thanks,
-- 
Mersenne Law LLP  ·  www.mersenne.com  ·  +1-503-679-1671
- Small Business, Startup and Intellectual Property Law -
9600 S.W. Oak Street · Suite 500 · Tigard, Oregon  97223

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