[gta02-core] Modem schematic / RF help needed

Dave Ball openmoko at underhand.org
Mon Sep 7 13:43:42 CEST 2009

Werner Almesberger wrote:
> 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.

Modem ON/OFF or RESET?  Telit expects ON/OFF to be asserted low for 1 
second to activate, so that might be less of a concern than reset (which 
only needs to be help low for 200ms)

Should the modem be powered from VBAT or VB_GSM?  I've just noticed that 
I had assumed the latter, but looking at U1750, VB_GSM is on the battery 
side of the switch, where VBAT is actually the switched supply.

We've also dropped the over current detection (nGSM_OC) in -core, was 
that intentional?  If so, is there any reason to keep R1751, R1753, C1753?

All the best,


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