Full-Featured µP Supervisory Circuit with ±1.5% Reset Accuracy

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, SO, and TSSOP packages, and provides the following functions:

* 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.

* Active-high RESET output.

* Manual-reset input.

* 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.

* Backup-battery switchover for CMOS RAM, real-time clocks, µPs, or other low-power logic.

* Write protection of CMOS RAM or EEPROM.

* 2.275V threshold detector provides for power-fail warning and low-battery detection, or monitors a power supply other than +5V.

* BATT OK status flag indicates that the backup-battery voltage is above +2.275V.

* Watchdog-fault outputasserted if the watchdog input has not been toggled within a preset timeout period. Applications

* Computers: Desktop, Workstation, Server * Controllers * Critical µP Monitoring * Intelligent Instruments * Portable Battery-Powered Equipment

* Precision 4.675V (MAX807L), 4.425V (MAX807M), or 4.575V (MAX807N) Voltage Monitoring

* 200ms Power-OK/Reset Time Delay

* RESET-bar and RESET Outputs

* Independent Watchdog Timer

* 1µA Standby Current

* Power Switching

* 250mA in VCC Mode

* 20mA in Battery-Backup Mode

* On-Board Gating of Chip-Enable Signals;

* 2ns CE Gate Propagation Delay

* MaxCap® and SuperCap Compatible

* Voltage Monitor for Power Fail

* Backup-Battery Monitor

* Guaranteed active-low RESET Valid to VCC = 1V

* ±1.5% Low-Line Threshold Accuracy 52mV above Reset Threshold