CS8140 is a 5V watchdog regulator with protection circuitry and three logic control functions that allow a microprocessor to control its own power supply. The CS8140 is designed for use in automotive, switch mode power supply post regulator, and battery powered systems. Basic regulator performance characteristics include a low noise, low drift, 5V ± 4% precision output voltage with low dropout voltage (1.25V @ IOUT = 500mA) and low quiescent current (7mA @ IOUT = 500mA). On board short circuit, thermal, and overvoltage protection make it possible to use this regulator in particularly harsh operating environments. The Watchdog logic function monitors an input signal (WDI) from the microprocessor or other signal source. When the signal frequency moves outside externally programmable window limits, a signal is generated ( ). An external capacitor (CDELAY) programs the watchdog window frequency limits as well as the power on reset (POR) and delay. The function is activated by any of three conditions: the watchdog signal moves outside of its preset limits; the output voltage drops out of regulation by more than 4.5%; or the IC is in its power up sequence. The signal is independent of VIN and reliable down to VOUT = 1V. In conjunction with the Watchdog, the ENABLE function controls the regulator’s power consumption. The CS8140’s output stage and its attendant circuitry are enabled by setting the ENABLE lead high. The regulator goes into sleep mode (IOUT = 0mA) until the next watchdog signal arrives, which is brought in through the WDI pin. This function can prevent the output voltage of the regulator from drifting away from its normal output voltage when it is unattended. The ENABLE function can also be used to save power.