Devices and methods for detecting the plug-in of an accessory device by a host device are provided. A host device includes a power switch coupled between a battery and a processor. The host device is turned off by a power button coupled to the power switch. A capacitive sensing circuit is coupled to a signal line of a host device port, and is configured to detect a plug-in of the accessory device by monitoring an input capacitance of the signal line. A logic circuit is coupled to an output of the power button and to an output of the capacitive sensing circuit, and the logic circuit turns on the power switch if the power button is in an on position or if the capacitive sensing circuit detects a plug-in of the accessory device.