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MAX791：Microprocessor Supervisory Circuit

Full-Function µP Supervisory Circuit

The MAX791 microprocessor (µP) supervisory circuit reduces the complexity and number of components needed to monitor power-supply and battery-control functions in µP systems. The 50µA supply current makes the MAX791 ideal for use in portable equipment, while the 6ns chip-enable propagation delay and 250mA output capability (25mA in battery-backup mode) make it suitable for larger, higher-performance equipment. The MAX791 comes in 16-pin DIP and narrow SO packages and provides the following functions: µP reset-RESET-bar output is asserted during power-up, power-down, and brownout conditions, and is guaranteed to be in the correct state for VCC down to 1V, even with no battery in the circuit. Manual-reset input. A 1.25V threshold detector provides for power-fail warning and low-battery detection, or monitors a power supply other than +5V. Two-stage power-fail warning-a separate low-line comparator compares VCC to a threshold 150mV above the reset threshold. Backup-battery switchover for CMOS RAM, real-time clocks, µPs, or other low-power logic. Software monitoring of backup-battery voltage. A watchdog-fault output is asserted if the watchdog input has not been toggled within either a preset or an adjustable timeout period. Write protection of CMOS RAM or EEPROM. Pulsed watchdog output, to give advance warning of impending WDO-bar assertion caused by watchdog timeout.

Key Features Precision 4.65V Voltage Monitoring 200ms Power-OK/Reset Time Delay Independent Watchdog Timer-Preset or Adjustable 1µA Standby Current Power Switching 250mA Output in VCC Mode 25mA Output in Battery-Backup Mode On-Board Gating of Chip-Enable Signals Memory Write-Cycle Completion 6ns CE Gate Propagation Delay MaxCap™ or SuperCap™ Compatible Voltage Monitor for Power-Fail or Low-Battery Warning Backup-Battery Monitor Guaranteed RESET-bar Valid to VCC = 1V

MAX791: Typical Operating Circuit Applications/Uses Computers: Desktop, Workstation, Server Controllers Critical µP Monitoring Intelligent Instruments Portable Battery-Powered Equipment

DataSheet

Parametrics

Quality and Environmental Data

• MAX791.pdf

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