[gta02-core] Modem schematic / RF help needed

Werner Almesberger werner at openmoko.org
Mon Sep 7 11:35:25 CEST 2009

Rask Ingemann Lambertsen wrote:
> Basicly, expect glitches on the SC32442B GPIOs when going into
> suspend mode.

Hmm, I've never heard of GPIO problems when going into CPU suspend.
There have been a severe issue in GTA01 with current still going
into the CPU when powering down (PMU Standby) and causing the CPU
to emit transients.

The problems was that such transients could cause the modem's reset
line to be asserted, via that transistor. This in turn brought the
modem out of "power off", and it happily started to burn power,
even though the system was supposedly off.

We've never seen that problem with GTA02. That may be because GTA02
has that modem "power switch" (U1705). I think it can't hurt to
route the modem's reset signal to a PMU GPIO, to make sure it's
stable even if we cut power to the CPU.

- Werner

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