Output driver with current compensation circuit for variation of common mode voltage

摘要

A current driver, a common mode voltage monitoring circuit and a current compensator are provided to drive a twisted pair cable, which is made up of two signal lines coupled to a terminal bias voltage through respective terminal resistors. The common mode voltage monitoring circuit monitors a difference between a common mode voltage of the twisted pair cable and a supply voltage level for the current driver. And the current compensator is coupled to the twisted pair cable to compensate for an output current of the current driver in accordance with a result of monitoring performed by the common mode voltage monitoring circuit. If the current driver has decreased its current drivability due to a drop of the supply voltage level of the current driver or a variation in the common mode voltage of the twisted pair cable, then the current compensator compensates for the decrease. Thus, the current driver can continuously operate in a broad voltage range to supply a constant current.