Archived from groups: alt.comp.hardware.homebuilt (
More info?)
Will Dormann <wdormann@yahoo.com.invalid> writes:
>Henry wrote:
>> I think its 12vdc at 55 amps
>So that makes what... 660 Watts output for a single USB port?
>Care to cite your source?
www.usb.org/developers/docs/ has usb_20.zip which is about as
readable as any other standard. Digging through that it appears
that the standard may allow different devices to supply different
amounts of current. The voltages are to be between 4.4 and 5.25
volts for devices that provide between, the minimum of, 8ma and
100ma. Above 100ma you must meet USB 2.0 specs and keep the
voltage between 4.75 and 5.25 volts.
So the 12 volt claim is out of line BUT if you were to carefully
read between the lines it MIGHT be possible to build and get
certified a USB 2.0 device that supplied 55 amps!