On Mon, 1 Jun 1998 15:13:45 -0300, you wrote:

>Perhaps someone can help me with this one -
>
>I am considering using 2, 3V lithium batteries (coin cells) to power a
>small PIC based device - the unit will be powered all the time and will be
>in slep mode most of the time - coming out when a button is pressed to wake
>it up on port B <7:4>.  The two cells will be placed in one of those
>"double height" PC board holders.
>
>My question is this - with the cells powering the PIC directly (i.e. no
>regulator etc.), am I going to run into trouble with the thing when the
>user replaces the cells as one will be placed in the holder first , then
>the second.  I checked the holder and the clips do grab a single cell,
>thereby presenting 3V to the micro for a period of time before the second
>cell is inserted.  There won't be any brown out or watchdog.  Am I likely
>to cause the micro to "fetch up" with this preactice?  Perhaps there is a
>common "rule of thumb" that I am missing here - I haven't designed a device
>like this before.
>
>Thanks for any help peopl can provide.
>
>Lewis
>cobb@zeus.ee.unb.ca
>
>PS - there are no other circuits to worry about for the most part in this
>unit as all other circuitry is powered from the micro's port pins.
The PIC will almost certainly run OK at 3V the LC versions are just
_tested_ to run at low voltage over the full temp range, the chip is
the same.
     ____                                                           ____
   _/ L_/  Mike Harrison / White Wing Logic / wwl@netcomuk.co.uk  _/ L_/
 _/ W_/  Hardware & Software design / PCB Design / Consultancy  _/ W_/
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