Common mode stabilization circuit for differential bus networks

Abstract

A differential bus network, in general, or a controller area network (CAN) driver, in particular, controls and minimizes the variation on the common-mode signal of the CAN bus. This CAN driver also provides improved symmetry between its differential output signals, CANH and CANL, and provides protection for its low voltage devices from voltage transients occurring on its output lines. The common-mode signal is sensed and buffered, then during the dominant to recessive transition, the bus signals are shorted to the buffered common mode voltage. Specifically, additional switches or transistors are used to pull the differential output signals, CANH and CANL, to the common mode signal Vwhen the state of the CAN bus transitions from dominant to recessive. This improvement minimizes high frequency spikes in the common-mode signal and eliminates DC shifts during transitions of the state of the CAN bus. A driver system may include a plurality of CAN drivers are serially interconnected to form a driver system, wherein each downstream driver stage receives a time-delayed form of the digital input signal TxD, each stage providing a time-delayed contribution to the differential output signals of the overall driver system.