The LTC690 family provides complete power supply monitoring and battery control functions for microprocessor reset, battery back-up, CMOS RAM write protection, power failure warning and watchdog timing. A precise internal voltage reference and comparator circuit monitor the power supply line. When an out-of-tolerance condition occurs, the reset outputs are forced to active states and the chip enable output unconditionally write-protects external memory. In addition, the RESET output is guaranteed to remain logic low even with VCC as low as 1V.