GSM power usage / standby time

Ian Stirling OpenMoko at
Sat Dec 1 04:54:03 CET 2007

Wally Ritchie wrote:
> On Nov 15, 2007 10:47 AM, Erland Lewin <erland at> wrote:
>> I was looking at the power management page on the OpenMoko Wiki, which
>> says that the GSM part draws 45 mW when idle but connected (that's for
>> the GTA01, but I think the GTA02 has the same GSM chipset), and that the
>> bGattery capacity after power supply losses is 3.5 Wh. This would give a
>> theoretical maximal standby time of about 3 days (in practice lower
>> because I guess things like RAM refresh will use power too).
> In GSM idle mode the power consumption should be < 10mW from the
> modem. This is based on similar devices using this chipset.
> If all other devices are off or suspended, then the only other thing running
> would be SDRAM self-refesh and the PMU, both of which are minimal.
> That being said, we still seem to be a long way from fully working
> suspend/resume which would put the modem in low power state as well as
> all other devices.

Unfortunately, that seems not to be the case.

Send at at poff to the modem.
Approximately 100uA being drawn.
Leave modem alive
Approximately 50mW being drawn.

It seems obvious that the current is not being drawn by 'the usual 
suspects' - a bit of the phone not turning off properly, but it must be 
either the modem, or something directly connected to the modem.

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