[gta02-core] revisiting ECN0040 (backup battery)

Werner Almesberger werner at openmoko.org
Fri Apr 9 19:05:05 CEST 2010

The backup battery situation merits a second look. In addition to
the material already in ECN0040, we have the recent survey that
quite strongly suggests that the backup battery simply is no good,
and that the problems may not just be caused by regular aging (as
I assumed in ECN0040.)

See also my comment here:

So I think the case for removing the backup battery is getting
stronger. I also very much like the idea of having a PMU reset
state that doesn't depend on what the system did before the

We have a capacitor to keep up the modem's RTC, so there's at
least one RTC in the system that reliably survives a complete loss
of power for a short while.

Does anyone want to save the backup battery ?

If not, what do we put in its stead ? Choices include nothing or a
resistor. The backup battery charger can be turned off, so no
power would be lost in the resistor under normal conditions.

- Werner

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