[sdiy] Battery backup

[Colin f]

> But, now i need a battery backup
> circuit for the SRAM. What's the easiest methode and
> how do i shield the power from the battery not to leak
> out to the rest of the circuitry, draining the battery
> in no-time? Should i build in a charge-circuit or
> what? Google doesn't give much...

By far the easiest method, though not the cheapest, is to use a Dallas/Maxim
DS1210 battery backup controller IC.
Google the part number for the datasheet.
This IC has the advantages of supporting dual batteries, and providing a
method for the CPU to detect low battery condition.
Recharging is rather pointless considering the long life of lithium cells,
and the risk of leakage.

Cheers,
Colin f