] USB connector is designed to feed power up to 100 mA 5V
] power to the devices connected to it. The power is fed
] though Vbus and GND pins. The host USB pert can supply up
] to 500 mA at voltage at least 4.75 V (for the HUB to be
] able to power 4 port HUB which can supply up 100 mA at
] voltage of at least 4.40V). The USB port does not need to
] supply more than 100 mA unless the device connected to it
] requests more current. UL overcurrent-prevention
] requirement says that no USB port ever pass more than 5A
] onto any port (short circuit protection to avoid damage
] to equipments and wiring).

Reference to myself: Check effect on other USB devices when sourcing ~2A.

Power circuits from PC componenets