LTC690

Features n Guaranteed Reset Assertion at VCC = 1V n 1.5mA Maximum Supply Current n Fast (35ns Max) Onboard Gating of RAM Chip Enable Signals n SO-8 and S16 Packaging n 4.65V Precision Voltage Monitor n Power OK/Reset Time Delay: 50ms, 200ms or Adjustable n Minimum External Component Count n 1µA Maximum Standby Current n Voltage Monitor for Power-Fail or Low Battery Warning n Thermal Limiting n Performance Specified Over Temperature n Superior Upgrade for MAX690 Family Applications n Critical µP Power Monitoring n Intelligent Instruments n Battery-Powered Computers and Controllers n Automotive Systems LTC690/LTC691 LTC694/LTC695 Microprocessor Supervisory Circuits Description The LTC®690 family, LTC690/LTC691/LTC694/LTC695, provides complete power supply monitoring and battery control functions for microprocessor reset, battery backup, 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. The LTC690 family powers the active CMOS RAMs with a charge pumped NMOS power switch to achieve low drop­ out and low supply current. When primary power is lost, auxiliary power, connected to the battery input pin,...