Wifi / GSM logic powerdown while device on

Andy Green andy at openmoko.com
Wed Aug 20 11:51:01 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:
| On 8/20/08, Andy Green <andy at openmoko.com> wrote:
|>  So, which pins still have any high level that can feed GSM side through
|>  protection diodes in this situation?  CPU doesn't have any rail
above 0V...
| Sorry for herding goats.


| MY understanding was we talk about
|   CPU up _and_  GSM down.
| i.e. airplane (save) mode or some other conserving mode.

Joerg definitely wasn't talking about that when you replied to him
starting this subthread:

''This power removal is done by U1705, and it should relyably cut power
when we disable IO_3V3 what is quite normal for shutoff.''

For GSM off state with everything else powered, as I said it would be
more certain if we had the power to the PA switched but we don't.

Looking at leakage, the only path seems to be UART TX and handshake
output side stuff from CPU being high.  The power-on thing is by an NPN
transistor that is OC when off.  So I guess it's true if we don't take
care to put these to GPIO output '0' when we turn GSM off, we ought to
do it, for the reason you mention.

- -Andy
Version: GnuPG v1.4.9 (GNU/Linux)
Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org


More information about the hardware mailing list