The Atmel-ICE is powered by the USB bus voltage. It requires less than 100mA to operate, and can therefore be powered through a USB hub. The power LED will illuminate when the unit is plugged in. When not connected in an active programming or debugging session, the unit will enter low-power consumption mode to preserve your computer's battery. The Atmel-ICE cannot be powered down - it should be unplugged when not in use.