> 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.
>
As a variation on this theme what about using a Raytheon RC4190 micropower
Switching Regulator as a battery extender.
With a 6 volt battery you could let the battery voltage drop to 5 volts when
the regulator would kick in holding the output at 5 volts right down to a
battery voltage of 1.8 volts. There is also an additional bonus of a low
battery output that would go low at 2.2 volts. The supply current required
by this IC is 215uA and the input voltage range 2.2 to 24 volts, switch
current 200mA. Instead of a 6 volt battery, use a 4.5 volt but keep the
output at 5 volt.

Regards

Chris Carr

P.S. I think the colon after [PIC] was missing in the subject line.

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