Patent ID: 8456784

Claim:
An overvoltage protection circuit comprising: a reference voltage generator for providing a reference voltage that is relatively constant during an overvoltage event, wherein the reference voltage generator comprises: a first filter circuit for filtering transients in a voltage signal on the first power supply terminal; and a timer circuit coupled to the first filter circuit, the timer circuit for maintaining the reference voltage for a predetermined time period; a trigger circuit coupled to receive the reference voltage and a first power supply voltage, the trigger circuit for comparing the reference voltage to the first power supply voltage, and in response to detecting that the first power supply voltage is above the reference voltage, the trigger circuit providing a trigger signal having a voltage proportional to a voltage level of the overvoltage event; and a clamping device coupled between a first power supply terminal and a second power supply terminal, the clamping device for providing a current path between the first and second power supply terminals in response to the trigger signal.