No battery Vsys issue is USB overcurrent?

Joerg Reisenweber joerg at
Mon Jun 30 17:07:39 CEST 2008

Am Mo  30. Juni 2008 schrieb Andy Green:
> |> Currently the hypothesis I am trying to work with is that we pull way
> |> too much current at power up, and the loss of Vsys is a reasonable
> |> response from the pcf50633.
> |
> | That sounds plausible, yes. I estimated that the systems draws about
> | 3W from the capacitor bypassing VB_SYS.
> Wah for how long though?
> |> So where does all the power go?  I didn't find out yet (or indeed prove
> |> it is true).
> |>
> |
> |> I sniffed around the GSM stuff for a while, because the charger action
> |> can basically power it all since it is directly powered from "battery",
> |
> | Ah, that's an interesting theory. The PMU's GPIOs are stable in
> | Standby, so you could control the GSM power switch. However, our
> | default should already do this right.
> |
> | There's something we don't control with this switch, and that's the
> | RF amplifier. A radical way to test whether GSM is to blame would be
> | to remove B1701 and see what happens.
> I checked the enable for it last night, nothing. 

I think it's a great idea to remove/break B1701. RF-power-amp might draw a 
spike, no matter whether there are enable-spikes anywhere at all.

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