The CS8151 is a precision 5.0 V, 100 mA micro-power voltage regulator with very low quiescent current (400 mA typical at 200 mA load). The 5.0 V output is accurate within +/-2% and supplies 100 mA of load current with a typical dropout voltage of 400 mV. Microprocessor control logic includes Watchdog, Wake Up and RESETbar. This unique combination of low quiescent current and full microprocessor control makes the CS8151 ideal for use in battery operated, microprocessor controlled equipment. The CS8151 Wake Up function brings the microprocessor out of Sleep mode. The microprocessor in turn, signals its Wake Up status back to the CS8151 by issuing a Watchdog signal. The Watchdog logic function monitors an input signal (WDI) from the microprocessor. The CS8151 responds to the falling edge of the Watchdog signal which it expects at least once during each wake-up period. When the correct Watchdog signal is received, a falling edge is issued on the wake-up signal line. RESETbar is independent of VIN and operates correctly to an output voltage as low as 1.0 V. A RESETbar signal is issued in any of three situations. During power up the RESETbar is held low until the output voltage is in regulation. During operation if the output voltage shifts below the regulation limits, the RESETbar toggles low and remains low until proper output voltage regulation is restored. And finally, a RESETbar signal is issued if the regulator does not receive a Watchdog signal within the Wake Up period. The RESETbar pulse width, Wake Up signal frequency, and Wake Up delay time are all set by one external capacitor CDelay. The regulator is protected against short circuit, over voltage, and thermal runaway conditions. The device can withstand 74 volt peak transients, making it suitable for use in automotive environments.