[PATCH 1/1] uboot-pcf50633-default-curr-lim-1A.patch

Andy Green andy at openmoko.com
Fri Feb 22 04:11:14 CET 2008

Hash: SHA1

Somebody in the thread at some point said:

> I would like to echo what I wrote a month ago at
> <http://bugzilla.openmoko.org/cgi-bin/bugzilla/show_bug.cgi?id=956>
> and point out that the USB Battery Charging specification
> <http://www.usb.org/developers/devclass_docs/batt_charging_1_0.zip>
> allows devices to draw up to 1.5 amperes from a special charger.
> Special chargers identify themselves by shorting the data lines.
> If the data lines aren't shorted, then you are limited to 100 or 500 mA,
> as Mr. Welte notes.  I hope that the OpenMoko wall charger will actually
> short the data lines; I do not understand why the bug report mentions
> some 48k resistor.

Well we use a magic resistor on an extra line of the connector to
indicate we have a magic 1A-capable charger attached.

> Based on my understanding of the USB battery charging specification,
> the "special charger" section of
> Nokia_2-mm_DC_Charging_Interface_Specification_v1_2_en.pdf
> (available from nokia.com) and on my measurements of some old
> phones of the Nokia DCT-3 series (3.5mm charging connector), 
> I believe that a current-limited 5.0-volt power supply at 500+ mA
> will work for all three classes of devices.

Well it is interesting but the charger thing is a done deal for us
already and it is okay as far as it goes.  It would have been nicer to
use this standard method, but if as Harald says if it turned up too late
to use it, well its okay.

> to load.  The nominal output current of the SON28 that I have in my bike
> <http://www.nabendynamo.de> is 580 mA.  If the current limit in the

Its a lot of power!  But this is just a matter of regulation before
giving it to the device.

- -Andy
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