Andrew,
Thanks for the suggestion.  I looked at your app note.  On your appnote the
battery is not regulated at all.  The regulator is for outside power only.
On my application, I only have battery power.  My delima is how to get full
use of 2X3VDC = 6VDC with a PIC that specs 5.5VDC max.
I have recently been looking at LDO regulators as per suggestions on the
list.  They consume a small amount of power when on.  Some have a turn-off
input that makes it almost no current.  This interests me, but I have not
found a low part count way to have a PIC turn its self off using this and
able to wake from sleep.

This has become much to complicated.  A diode off the battery is what I am
using for now.

Best regards,
Giles



>FYI, there's a design on our website in App Note AN-6 that has a
>PIC12C509A running off either 3xAA (4.5V) or external 6-26Vdc. It
>uses an LM2941 regulator on the unregulated DC mainly for low dropout
>and reverse-hookup protection.
>
>The kicker in getting it to work in this environment was to put a
>diode in series with the output of the regulator -- this blocked the
>massive (10mA) drain on the battery side of things when there was no
>external input to the regulator. Also,  the battery ground is lifted
>when external power is applied. With that series diode, the current
>drain from the batteries in sleep mode is what you'd expect from the
>PIC alone.  I have a couple of these little Fan Controllers still
>running on their original batteries, which were installed in April
>2001.
>
>Another nice thing about this scheme is that the nominal voltage when
>running from external supplies is very close to that of a set of new
>batteries (around 4.4V).
>
>Anyway, this may give you some ideas ...
>   Andrew E. Kalman, Ph.D.   aek@pumpkininc.com
>


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