A Monolithic Quad Line Driver for Industrial Applications

The device described in this paper is a new quad line driver to be used in the hostile and noisy industrial environment and developed in mixed technology (BCD: Bipolar, Cmos, Dmos). It consists of four independent line drivers, each of which has a rail-to-rail push-pull output stage realized with power DMOS transistors connected in half bridge configuration. Even though the device is designed to be mainly used in the output cards of programmable controllers, it is a general purpose device since it can drive any kind of load (resistive, capacitive or inductive) with an output current of 100 mA. The novel structure of the top driver allows full protection of the output stage against any kind of short circuits and/or overloads providing a linear current limitation. Futhermore when a channel is tristated, for every applied voltage ranging from ground to the supply voltage, virtually zero current is absorbed from the output. A novel high efficiency central charge pump circuit has also been designed and implemented making possible a very wide supply voltage operation (6 to 50 V) and high switching frequency (up to 500 KHz). The device can allso be used as a receiver since the imput voltage can swing from -10 to 50 V.