No battery Vsys issue is USB overcurrent?

Andy Green andy at
Mon Jun 30 18:58:32 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:
| Andy Green wrote:
|> No need, everything that happens on there is synchronous to pcf50633
|> 32kHz clock... these two in the pic are locked together.
| It does make sense if the start of all this is synchronized with some
| clock. However, doesn't the duration of the Vsys drop event change
| when you add an external capacitor ? It does in my experiments.

Yeah it does change the slope of the V part, so it's not all tick-tock.
~ But it remains locked to pcf50633 32kHz.... the whole thing on Vsys is
managed by the pcf logically.

What fits it is it throws out Vsys "permanently" for whatever reason
(overcurrent on USB is the guess), and that is only countermanded when
Vsys goes below 2V (lowsys action I guess).  How long it takes to hit 2V
on the downward part of the V once Vsys is no longer driven by anything
is just a function of the capacitive load on Vsys.

The Vsys comes back, and again the time taken to charge the capacitors
on Vsys defines the slope back up again, that's why it's symmetrical.

- -Andy
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