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LTC692 - Microprocessor Supervisory Circuits

The LTC692/LTC693 provide 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 LTC692/LTC693 power the active CMOS RAMs with a charge-pumped NMOS power switch to achieve low dropout and low supply current. When primary power is lost, auxiliary power, connected to the battery input pin, powers the RAMs in standby through an efficient PMOS switch.

For an early warning of impending power failure, the LTC692/LTC693 provide an internal comparator with a user-defined threshold. An internal watchdog timer is also available, which forces the reset pins to active states when the watchdog input is not toggled prior to a preset timeout period.

Features Guaranteed Reset Assertion at VCC = 1V 1.5mA Maximum Supply Current Fast (35ns Maximum) Onboard Gating of RAM Chip Enable Signals 4.40V Precision Voltage Monitor Power OK/Reset Time Delay: 200ms or Adjustable Minimum External Component Count 1μA Maximum Standby Current Voltage Monitor for Power-Fail or Low Battery Warning Thermal Limiting Performance Specified Over Temperature Superior Upgrade for MAX690 Family SO8 and SO16 Packaging Typical Application

Applications Critical μP Power Monitoring Intelligent Instruments Battery-Powered Computers and Controllers Automotive Systems Packaging

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