Patent ID: 7521966

Claim:
An apparatus including a universal serial bus (USB) transmitter comprising: a USB port including a data pin; a PMOS pullup transistor having a first terminal connected to a first voltage supply, and a second terminal coupled to the data pin; first means for transmitting a pullup data signal to a gate terminal of the pullup transistor such that the pullup data signal is one of a first low voltage level and a first high voltage level; an NMOS pulldown transistor having a first terminal connected to a second voltage supply and a second terminal coupled to the data pin; and second means for transmitting a pulldown data signal to a gate terminal of the pulldown transistor such that the pullup data signal is one of a second low voltage level and a second high voltage level, wherein the first low voltage level is greater than the second low voltage level, wherein the first high voltage level is greater than the second high voltage level, wherein the USB transmitter further comprises a PMOS cascode transistor coupled between the second terminal of the PMOS pullup transistor and the data pin, and wherein the USB transmitter further comprises bias/protection means for applying a bias/protection signal to a gate terminal of the PMOS cascode transistor during normal operation, and for passing a third high voltage level from the data pin to a gate terminal of the PMOS cascode transistor when the third high voltage level is greater than the first high voltage level.