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A "Dedicated Charging Port" is intended to be a port that is only a charger/power-source and does not have any USB functionality. The D+ and D- pins are shorted together on this port to indicate that it is a dedicated charging port. The downstream device, the iPad in this case, detects that the D+ and D- pins are shorted together and that it is OK to draw up to 1.8A (9W at 5V) from the bus.
However, that is not the only way a device can legally draw more than 5W from a port. The Battery Charger spec defines some other modes as well that allow a device to negotiate up to 1.5A (7.5W at 5V) of current from a compliant bug and draw this current while also communicating on the bus.
Regards,
Hamid
billhogarty wrote:
For Hamid:
Appreciate your detailed explanation on this topic.
One question: When a hub or charger has a "dedicated charging capability", is it identified in any special way?
Thanks, Bill Hogarty
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