force usb charge current

Werner Almesberger werner at
Tue Jan 27 23:08:12 CET 2009

C?dric Berger wrote:
> Is it possible to set allowed current to arbitrary value, or at least
> 350mA or 750mA ?

Let me try a variation of Andy's reply: No, but you can get closer
than it seems ;-)

100/500/1000mA are nominal values. The typical actual limit is a
bit lower, namely 90/450/900mA, see table 91 of

So the 350mA car charger may be up it. Also, if it's specified at
350mA, this doesn't mean that it'll self-destruct if you draw 351mA.
You're more likely to experience a gradual reduction of performance,
e.g., a voltage drop. The PMU tolerates a drop down to about 4V
before it ignores USB power.

Since you have a number of these chargers, you may well take the
risk of damaging one by driving it beyond specs. The only thing to
really worry about would be a failure mode in which the charger
emits more than 5.5V, because this could damage the PMU.

- Werner

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