[time-nuts] Motorola Oncore UT+ firmware upgrade & backup power questions

[Attila Kinali]

On Sun, 15 Mar 2015 03:27:06 -0700
Hal Murray <hmurray at megapathdsl.net> wrote:

> attila at kinali.ch said:
> > A CR2032 is a quite huge coin cell. An NVRAM module does not use much power
> > once Vcc goes to zero. In todays low power modules it's in the order of
> > 100nA max specified. You can assume it to be somewhere in the range of 10nA
> > (probably package leakage limited) and 1uA (something has gone wrong or very
> > old module). ... 
> 
> GPS also needs the time, so add on a 32KHz clock.

Oops.. right. I totally forgot that. Then it's somewhere in the
range of 0.2uA (modern RTC's with NVRAM) to 10uA (really old ones).
RTCs do not use that much current as one might think. I "recently"
did a MSP430FR5736 based system that had its RTC running and was
powered by two SR48 coin cells (~80mAh). Total expected lifetime
was 1.5y with all the stuff it had to do. IIRC minimum current
consumption we measured was 2.6uA(+/-0.5uA measurement accuracy,
total of the whole device).

			Attila Kinali

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