[Gta04-owner] GTA04 power management.

NeilBrown neilb at suse.de
Sat Dec 24 13:49:28 CET 2011

On Sat, 24 Dec 2011 12:45:48 +0100 "Dr. H. Nikolaus Schaller"
<hns at goldelico.com> wrote:

> >> 
> >> So that suggests around 90mA still being used by something else.
> Hm. This reminds me on the power demand of the Boot-ROM mode. I.e. before
> U-Boot starts.
> >> 
> >> I've turned off the power supplies for WIFI, BT, GPS antenna, sensors.
> >> I've turned off VDD1 and VDD2 to the CPU, and the various power supplies
> >> for USB and the battery charger (VINTANA, VINTDIG).  All the leds are off.
> >> 
> >> All that should be left on are VDDIO aka 1V8, and REGEN aka 3v3.  It seems
> >> that these need to be on by design.
> >> 
> >> With the GPS off (it is, I checked) and the LEDs off and none of the
> >> other peripherals enabled, 3V3 shouldn't be providing much current as
> >> discussed previously.  The only things of any significance I can see
> >> driven 1V8 are:
> >> 
> >>  - The 26MHz clock.  This seems to be on all the time where I (naively)
> >>    would have expected it to be enabled by the CLKEN output from the
> >> TWL4030. I assume there is a reason for that?  How much current does it
> >> use?
> I think this isn't very much but will check in the next days. Maybe this could
> be improved for future board revisions since the 26 MHz clock has a separate
> enable input which could also be controlled by the CLKEN.
> Currently the TPS65950/TWL4030 chip should just gate the clock so that
> it is removed from the CPU.

I think I've got it doing that.  It is separate from the other power
resources (in P3 rather than P1, hence controlled by CLKREQ rather than
NSLEEP1) but should be being turned off.

> >> 
> >>  - Some power to the CPU.  If I read it correctly it is only supplying
> >>    - DDS - the display subsystem
> >>    - POP-DDR and POP_FLASH - the Package on Package memory.
> >> 
> >>    I would expect the DDS to be off (not sure how to check yet) and the
> What I don't know for sure is if the code to control the TD028 display is
> completely correct. I.e. it may not correctly switch off the LDOs within the
> display module.
> But you could easily test that by operating the GTA04 without display.

I haven't yet tried plugging in a display...

> >>    memory to be in self-refresh mode.
> Memory in self-refresh could be some reason.
> >> Any guesses were that 90mA is going?  I would understand a 10mA draw, but
> >> 90mA seems a bit steep for a sleeping device.
> One voltage that is not shown in your list is VMMC. The SD card may draw
> some current.

That is being turned off by the mmc module when it prepares for suspend.


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