Thread: USB Wall Charger
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Old 07-13-2010, 02:11 AM   #32
DNSB
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Maximum current from USB ports
Quote:
Originally Posted by 3d0g View Post
The USB spec is no longer 500mA. It's actually quite complicated now as there was an IEEE USB Battery Charging Spec started back in 2006 (as I recall), that allows up to 1.5A over USB. Devices negotiate how much they need / can get from the host. So, for a true USB host port, the USB device (kobo) will sort out how much it can have. For a "dumb" USB wall-charger, you'll want to be able to deliver the full rated requirement of 700mA.
I seem to remember it 1.5A at low speed, 900mA at high speed and whatever current can be safely supplied when there is no data communication.

Your definition of safely may not be the same.

My motherboard uses (I think) self-resetting fuses that open after about 6 minutes at 650mA and take about 5 minutes to reset under no load conditions.
Last edited by DNSB; 07-13-2010 at 02:16 AM.
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