Thread: USB Wall Charger
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Old 07-11-2010, 07:06 PM   #27
DaleDe
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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.
Actually there is no requirement for USB to deliver more than 500mA and anyone who expects a computer to power their device cannot guarantee that more than 500 mA is available. So although the spec has some complicated variations and under certain conditions might only be able to supply 100mA to a given device the 500mA is certainly a reasonable minimum if you don't use a hub. You cannot expect any computer to supply 1.5 A. You might get it but then again you might not.

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