Patent ID: 8166222

Claim:
A microcontroller unit, comprising: a processing core; a USB interface for providing USB communications between the microcontroller unit and an external USB device and having an operating voltage below 5V; USB transceiver circuitry for transmitting data to/from the microcontroller unit, wherein the USB transceiver circuitry provides protection to the USB interface against a 5V short circuit, wherein the transceiver circuitry further comprises: at least one receiver connected to an output pin of the USB interface; at least one driver providing an output on a driver output node connected to the output pin of the USB interface; voltage tolerance circuitry within the at least one driver for pulling the driver output node low with an active pull down circuit to protect output driving circuitry of the at least one driver responsive to the 5V short circuit on the output pin to protect against the 5V short circuit; and a USB controller for controlling operations of the USB transceiver circuitry responsive to instructions from the processing core.