Re: PXA27x UDC Power

[David Brownell <david-b@xxxxxxxxxxx>]

On Wednesday 28 November 2007, Thomi Aurel RUAG A wrote:
> AFAIK the Intel Xscale PXA27x doesn't support "a bus-powered device model"
> (see Intel PXA27x Processor Family Design Guide, chapter 12.4.2 Bus-Powered Device)
> 
> They argue, that the PXA27x cannot limit it's current consumption to less
> than 500uA in suspend mode. So my conclusion is that the PXA27x
> cannot be operated in bus-powered mode.
> 
> I would be pleased to hear if there is a solution/workaround.

That's very true, but he was talking about a self powered device.
It's got a battery, so it's not bus-powered.

A self-powered device is still allowed to draw power from the
USB host, and battery recharging is a very common reason to
do that.  Another is just to reduce the power drain on the
battery ... if your USB circuitry uses 50 mA and you can have
the host provide that, that's 50 mA less for your battery.

- Dave



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