CMOS OUTPUT DRIVER FOR SEMICONDUCTOR DEVICE AND RELATED METHOD FOR IMPROVING LATCH-UP IMMUNITY IN A CMOS OUTPUT DRIVER

摘要

An output driver circuit for a semiconductor device. In one embodiment, the output driver is coupled to an output terminal of the semiconductor device and consists of an N-channel pull-down transistor and a P-channel pull-up transistor formed in an N-well in a P-type substrate. A tie-down region formed in the N-well is selectively coupled to a supply potential by means of a decoupling transistor, and during normal operation of the driver maintains the supply voltage bias of the N-well. An overdrive detection circuit is coupled to the output terminal. Upon detection of an overdrive condition on the output terminal, such as a voltage exceeding a predetermined maximum, or excessive current injected into the output terminal (or both), the overdrive detection circuit deasserts a control signal applied to the gate of the decoupling transistor, thereby decoupling the N-well from the supply potential. In one embodiment, the decoupling transistor is not coupled to the output terminal.