MAX807L

19-0433; Rev 0; 9/95 Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy _______________General Description The MAX807 microprocessor (µP) supervisory circuit reduces the complexity and number of components needed to monitor power-supply and battery-control functions in µP systems. A 70µA supply current makes the MAX807 ideal for use in portable equipment, while a 2ns chip-enable propagation delay and 250mA output current capability (20mA in battery-backup mode) make it suitable for larger, higher-performance equipment. The MAX807 comes in 16-pin DIP and SO packages, and provides the following functions: 1) µP reset. The active-low RESET 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. 2) Active-high RESET output. 3) Manual-reset input. 4) Two-stage power-fail warning. A separate low-line comparator compares VCC to a threshold 52mV above the reset threshold. This low-line comparator is more accurate than those in previous µP supervisors. 5) Backup-battery switchover for CMOS RAM, real-time clocks, µPs, or other low-power logic. 6) Write protection of CMOS RAM or EEPROM. 7) 2.275V threshold detector—provides for power-fail warning and low-battery detection, or monitors a power supply other than +5V. 8) BATT OK status flag indicates that the backup-battery voltage is above 2.275V. 9) Watchdog-fault output—asserted if the watchdog input has not been toggled within a preset timeou...