Patent attributes
An apparatus includes a Universal Serial Bus (USB) transceiver of a USB host controller, a first pull-down resistor, a first switch, a second pull-down resistor, a second switch, and a detachment module. The USB transceiver has a differential output. The first switch electrically couples the first pull-down resistor to a positive terminal of the differential output in response to a first switch control signal. The second switch electrically couples the second pull-down resistor to a negative terminal of the differential output in response to a second switch control signal. The detachment module selectively determines whether a USB device is electrically coupled to the differential output by checking a voltage at the differential output while at least one of the first switch control signal or the second switch control signal is asserted. The detachment module determines whether the USB device is electrically coupled to the differential output by checking the positive terminal when the USB transceiver is in a full-speed idle state and by checking the negative terminal when the USB transceiver is in a low-speed idle state.
