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LTC694-3.3 - 3.3V Microprocessor Supervisory Circuits

The LTC694-3.3/LTC695-3.3 provide complete 3.3V power supply monitoring and battery control functions. These include power-on reset, battery back-up, RAM write protection, power failure warning and watchdog timing. The devices are pin compatible upgrades of the LTC694/LTC695 that are optimized for 3.3V systems. Operating power consumption has been reduced to 0.6mW (typical) and 3μW maximum in battery back-up mode. Microprocessor reset and memory write protection are provided when the supply falls below 2.9V. The RESET output is guaranteed to remain logic low with VCC as low as 1V.

The LTC694-3.3/LTC695-3.3 power the active 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 LTC694-3.3/LTC695-3.3 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 Pin Compatible with LTC694/LTC695 for 3.3V Systems 200μA Typical Supply Current Fast (30ns Typ) Onboard Gating of RAM Chip Enable Signals SO-8 and S16 Packages 2.90V 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 Typical Application

Applications 3.3V Low Power Systems Critical μP Power Monitoring Intelligent Instruments Battery-Powered Computers and Controllers Automotive Systems Packaging

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