Charging devices from USB ports

[meromeo]

There are many specitications on USB powered devices?.
That is: I´ve seen some chargers devoted to some particular devices (telephones, ipod, etc).
Aren´t the same requirements for charging?. If not, are regulated by any standard?.¡
Best regards.

[Jan Axelson]

The USB battery charging spec is here:

http://www.usb.org/developers/devclass_docs

It's been through a few revisions, which might explain some incompatibility. Ideally any USB charger would work with any device.

Jan

[Barry Twycross]

Also Apple invented their charging scheme before the USB-if came up with their charger spec. So iPod (and iPhone etc) chargers may be a different spec to other ones. Though later iPod and iPhone recognise USB-if chargers.