[gta02-core] Modem schematic / RF help needed

Rask Ingemann Lambertsen ccc94453 at vip.cybercity.dk
Fri Sep 11 23:48:09 CEST 2009

On Fri, Sep 11, 2009 at 04:10:41AM -0300, Werner Almesberger wrote:

> I'll feel much better about having the switch if it cuts all supplies
> and not leave the modem in a probably completely undesigned-for
> configuration.

   Me too.

> We could try the following approach:
> - bring back the switch (probably best to switch to the NTGD1100L
>   while we're at it) and a pull-up
> - route both VBATT and VBATT_PA through the switch
> - add a 0R resistor parallel to the switch. Put it somewhere where
>   it can be reworked. Since we feel confident, we make it NC for SMT.
> - we then need to free one of the PMU's GPIOs. MODEM_nON might be
>   the best choice, since the switch would override it anyway.
> - put a 0R into MODEM_nON from the CPU so that, in case of trouble,
>   we can fall back to the current configuration
> Does that sound good ?

   I was thinking of just connecting the switch in parallel with R8101
(currently 0R that we would make NC) and connecting the enable input
(ON/OFF) to the GSM_2V8 supply. But I have not checked the power sequencing
requirements of the GE865. Right now I'm also confused by the lack of a
connection from the GSM_2V8 supply to the modem. Does it have an internal
2.8 V LDO to derive the I/O voltage from the 3.8 V supply?

Rask Ingemann Lambertsen
Danish law requires addresses in e-mail to be logged and stored for a year

More information about the gta02-core mailing list