Voltage surge protection circuit

摘要

A protection circuit (100, 700) 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 (100, 700) comprises a sensor (120) for sensing a voltage increase on the first supply rail (Vcc). Such a sensor may be implemented as an RC element. The sensor (120) has an output coupled to a signal path for providing a detection signal on said path. The sensor (120) triggers a clamping circuit (180) 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 (160) is coupled between the sensor (120) and the clamping circuit (180) to amplify the detection signal for the clamping circuit (180). The protection circuit further comprises a hold circuit (140) for holding the control input of the pre-amplifying stage (160) 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 (180) and extending the activation of the clamping circuit beyond the termination of the detection signal, thus yielding a more efficient protection circuit (100, 700).

主权项

1. A protection circuit for protecting an integrated circuit having a first supply rail and a second supply rail from exposure to an excessive voltage, comprising:
a sensor for sensing a voltage increase on the first supply rail, the sensor having an output coupled to a signal path for providing a detection signal on said path; a clamping circuit for clamping the first supply rail to the second supply rail in response to the detection signal; a pre-amplifying stage having a control input coupled to the signal path and an output coupled to the clamping circuit; and a hold circuit for holding the control input of the pre-amplifying stage in an enabled state upon termination of the detection signal; wherein the sensor comprises a poly-Si based capacitor for storing a voltage value of the first supply rail, an amplifier for amplifying the charge stored in the poly-Si based capacitor, and a diode connected between the capacitor and the second supply rail, wherein the amplifier forms a current mirror with the diode.