Minimising battery drain

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Minimising battery drain

Post by SHughes_Fusion » Mon Jul 31, 2017 1:14 pm

I've got a circuit powered from a single cell LiPo battery which uses an LM3670 buck regulator to provide a 3.3V rail. That all seems to work well, but I was wondering if there is any scope to save power by being able to shut the regulator down and power the processor (18F46K22) directly from the battery.

The unit sits in sleep for the majority of the time, usually the operator will wake it for a few minutes maybe 10-15 times a day, the rest of the time I'm just polling the wake button in a sleep loop. While the peripherals all have low power shutdown, I'm thinking that being able to power them and the regulator down completely would be the best solution for lowest power.

However, I can't think of any way to do this... The processor interfaces with various 3.3V peripherals (RN42, SN65HVD72 etc) so if I run the processor directly from the battery all the time the levels will be incompatible.

The other question is, am I worrying too much about this? Will the base current of an 18F in sleep be sufficiently higher than that of an 18LF to negate any saving from shutting everything else down?

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