This overvoltage protection circuit (OVP) protects sensitive electronic circuitry from overvoltage transients or regulator failures when used in conjunction with an external "crowbar" SCR. The device senses the overvoltage condition and quickly "crowbars" or short circuits the supply, forcing the supply into current limiting or opening the fuse or circuit breaker.The protection voltage threshold is adjustable and the MC3423 can be programmed for minimum duration of overvoltage condition before tripping, thus supplying noise immunity.The MC3423 is essentially a "two terminal" system, therefore it can be used with either positive or negative supplies.