Motorboating == USB overcurrent -> emergency shutdown -> NoPower -> autostart

Werner Almesberger werner at
Mon Jun 30 19:37:29 CEST 2008

Andy Green wrote:
> I just saw my backup battery is at 0.4V.

Mine's at 1.52V and I've seen it retain PMU settings, so the phenomenon
does not depend on entering NoPower.

BTW, the trace isn't very symmetrical on my system. Recovery is about
twice as fast as the plunge into doom. (Also your screenshots show

> It can work out if during startup Vsys is going under Vth(sysmin) which
> is hardcoded at 2.5V, it forces an "emergency shutdown" and pushes us
> into SAVE -- that is what gets us the sticky power loss.  Then it goes
> under Vth(syspres) 2V limit and we "reset and enter the NoPower state".

Also dropping all the way down to 2V seems to be optional. I have
the end of the drop hover around 2.44V at the moment. (After shorting
the backup battery.)

- Werner

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