UNDERVOLTAGE PROTECTION SYSTEM

PURPOSE: An undervoltage protection system is provided to shunt a transient current resulting from undervoltage and overvoltage conditions occurring on a power rail. CONSTITUTION: An undervoltage protection circuit(104) is connected to a power supply(102) through a high voltage ESD circuit(110). An electronic device and circuit(112) is connected to the undervoltage protection circuit in parallel. The hight voltage ESD circuit includes a conventional ESD circuit, such as a diode stack, an SCR, an active clamp used to shunt an overvoltage transient condition on the power supply. A control circuit(106) controls a conduction state of a voltage transient shunt circuit(108), in response to the voltage state of the power supply. [Reference numerals] (102) Power supply; (106) Control circuit; (108) Voltage transient shunt circuit; (110) High voltage ESD circuit; (112) Electronic device and circuit; (AA) Undervoltage protective circuit