There has a bit of discussion about USB power supplies and various voltage levels mentioned so I thought I'd wade through the technical specifications for an answer.

The source I am using is “Universal Serial Bus Specification” Rev 2.0 (April 27, 2000) signed by Compaq, Hewlett-Packard, Intel, Lucent, Microsoft, NEC, and Philips. It can be found at www.usb.org/developers/docs/ as part of the usb_20_052709.zip file which is the definition for USB 2.0. References are to the document usb_20.pdf.

Power is supplied via Vbus and is between 4.75 and 5.25 for high powered hubs and 4.4 and 5.25 for low powered hubs (ref. 7.2.2 Voltage Drop Budget)

The data voltage values are low (Vol) 0.3v (max) and high (Voh) 2.8v (min) (ref. 7.1.1 USB Driver Characteristics).

A complete description of the various plugs can be found in Chapter 6. I can't find a definition of the “mini” USB plugs. I didn't look very hard as I had to get to work. From my experience there is quite a variation between various plugs. For example there are at least 3 versions of the original “mini” plug like the one used in, Motorola, Blackberry, and Garmin products.

For more information I refer you to the document usb_20.pdf, all 650 pages, which is included in the above mentioned zip file.