On Thu, 2010-12-09 at 08:44 -0500, V G wrote:
> I just tested the open circuit output voltage of the little 1 Amp AC char=
ger
> that you get with the phone. It has a USB host socket so you can plug in
> your USB cable directly.
>=20
> The +5 V line is reading 5.10 volts
> One data line is reading 2.70 volts.
> The other data line is reading 2.00 volts.
>=20
> A question: Since the data lines have to be set at a certain voltage (wit=
h
> resistor voltage dividers), and the battery pack voltage will vary betwee=
n
> 4.4 - 5.6 volts, how would I get a steady voltage on the data lines to te=
ll
> the iPhone to draw 1 Amp? Would I need to just stick a low power voltage
> regulator at around 3.0 or 3.3 volts and create a divider from there?

The iPhone isn't looking for a "steady voltage", it's looking for a
ratio between lines, exactly what using resistors gets you, so the
obvious solution? Use resistors.

--=20
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