Voltage surge protection circuit

Abstract

A protection circuit () is disclosed for protecting an integrated circuit having a first supply rail (Vcc) and a second supply rail (Vss) from exposure to an excessive voltage. The protection circuit () comprises a sensor () for sensing a voltage increase on the first supply rail (Vcc). Such a sensor may be implemented as an RC element. The sensor () has an output coupled to a signal path for providing a detection signal on said path. The sensor () triggers a clamping circuit () to clamp the first supply rail (Vcc) to the second supply rail (Vss) in response to the detection signal, which typically signals an ESD event on the supply rails. A pre-amplifying stage () is coupled between the sensor () and the clamping circuit () to amplify the detection signal for the clamping circuit (). The protection circuit further comprises a hold circuit () for holding the control input of the pre-amplifying stage () in an enabled state upon termination of the detection signal. Such a hold circuit may comprise a further RC element for accelerating the activation of the clamping circuit () and extending the activation of the clamping circuit beyond the termination of the detection signal, thus yielding a more efficient protection circuit ().