Lads -

After some due consideration and scouring of the microchip databook I have
decided that I am going to re-design a PIC into my battery powered product
and the current processor is getting heaved.  The wake-up on port b <7:4>
and the super low current in sleep mode made up my mind - I'm looking at
the 16C620 series as a likely candidate but the 16F84 could be used for
much of the development without having to play the "wait to erase" game...

The above having been proclaimed, I have a couple of questions that may
sound trivial for those that have been designing with this processor
already but I figure I'll pass them by in the interest of coming up the
curve quicker -

1) Is it just my mis-reading, but does the brown out enabled, turn the pic
into a current HOG in sleep mode?  i.e. from 1uA to 300+uA?

2) I will be powering the system from 2 lithium cells and would like to
detect a low battery without having to use a big$, low dropout, low
Quiescent I regulator.  I'm thinking of doing the following and wonder if
it sounds reasonable;
- Dedicate a port pin to the driving of a zener diode
- Feed this reference into one of the analog comparators on the '620 chip.
- Feed the raw Vdd battery voltage into the "on-chip" programmable
reference and tie it to the other comparator input line - programming this
reference for 2.4-2.5 volts.

3) If I protect the electronics from a reverse battery with a diode right
across the battery terminal, I will protect the electronics at the
sacrifice of the batteries - this is ok - but - can a lithium coin cell
source enough current to be of harm - i.e. heat, meltdown etc.?



Thanks a million for any assistance people can provide.  The micros look to
be just the ticket for many projects!

Lewis
cobb@zeus.ee.unb.ca