Juan,
I will check with the Powerbook teams. We should meet the spec,
but you should be aware that section 7.2.2 allows power to droop to
4.75V at 500mA. That is also at the end of the cable, so your
device could see even less voltage (i.e. 4.6V with a 125mV cable
loss).
David Ferguson
USB Software Team
Apple Computer
At 12:55 PM -0500 7/8/05, Juan Pertierra wrote:
Hello,
I am having a few users beta test my new high speed bus-powered
USB device intended to run only on the mac. During testing one
user has found that the device fails when he attempts to run the
device on his brand new 15" powerbook on battery power. He can
literally have the device functioning perfectly on DC power, and
then pull the plug and then it fails. What is confusing is that
I've done all the development for this device on a new 1.67Ghz 17"
Powerbook, and on the 17" it works fine, with or without DC
power. I can unplug the power while the device is running and I
don't have any trouble at all.
Is there any difference between the supplied power on the USB
ports of the powerbooks while on battery power? I thought they
where all rated up to 500ma and nothing should change when on
battery power. He has the same problem if he connects the device
while the computer is already on battery power.
I'm in the process of having him do more tests to find out exactly
how it fails, but i figured someone here might be able to help if
this is a hardware spec issue.
Thanks,
Juan
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