TX LINE DRIVER WITH COMMON MODE IDLE STATE AND SELECTABLE SLEW RATES

摘要

A transmit line driver with selectable slew rates and a common mode idle state comprises a capacitor array of selectable capacitors coupled between a line driver and a pre-driver wherein a slew rate may be selected by the selectable capacitors. A common mode idle state is provided by coupling a selectable switch (MOSFET in the described embodiment) to a mirror device that provides a bias current to the pre-driver wherein, when the bias current is removed by the switch, the pre-driver produces an output signal that is equal to the supply voltage for the circuit. Accordingly, a differential pair of the line driver are both biased on and provide a common mode idle state. The common mode idle state is equal to one half of an output signal magnitude for a logic one.