Universal serial bus transmitter

摘要

A Universal Serial Bus transmitter comprising a USBTXP input and a USBTXM input for receiving respective data signals, and a USBP driver and a USBM driver for applying the respective data signals to USBP and USBM wires respectively. The transmitter comprises a transmit signal generator responsive to an asserting edge of a signal at one of the USBP and USBM inputs to define a leading edge of a transmit signal (USBTXIP) and to a corresponding de-asserting edge of a signal at the other of the USBP and USBM inputs to define the subsequent trailing edge of said transmit signal (USBTXIP). Even if the duty cycles of the input signals USBTXP and USBTXM are substantially different from 50%, this does not cause unacceptable jitter of successive crossover points nor cause the crossover point voltage level to be outside the USB tolerance, centred on 50% of the voltage swings of the USBP and USBM signals.