I'm designing a handheld PIC-based device (a handheld GPS / nav.
unit). It'll be using a PIC18LF2620 and will be battery powered. I'd
like to give it a software power-on/off feature so I can use one of
the control buttons for power on/off rather than having a big ugly
power switch. I was wondering what circuits people would suggest?

Just to complicate the issue some parts of the circuit operate at 5V
and others need 3.3V. The 18LF2620 can operate at down to 2.0V but
when the circuit's in full-power mode it needs to be running at 5V. My
plan was to use a 6V Ni-MH battery pack with MAX883 and MAX884
regulators. These have a low dropout voltage and provide a shutdown
mode. I was thinking I could power the PIC through a schottky diode
off the 5V normally and then have an "off" mode where it's powered on
~3.6V (three Ni-MH cells) through a different schottky diode. The
"off" mode would power only the PIC which would be in sleep mode. A
button press on one of the interrupt-on-change lines would wake the
CPU and it would raise an output line to tell the regulators to power
up again.

Does this sound line a feasible plan? Is there an easier way of doing this?

Thanks,
Zik

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