Microprocessor Supervisory Circuits

The MAX690A/MAX692A/MAX802L/MAX802M/MAX805L reduce the complexity and number of components required for power-supply monitoring and battery-control functions in microprocessor (µP) systems. They significantly improve system reliability and accuracy compared to separate ICs or discrete components.

These parts provide four functions:

1) A reset output during power-up, power-down, and brownout conditions.

2) Battery-backup switching for CMOS RAM, CMOS µP, or other low-power logic.

3) A reset pulse if the optional watchdog timer has not been toggled within 1.6sec.

4) A 1.25V threshold detector for power-fail warning or low-battery detection, or to monitor a power supply other than +5V.

The parts differ in their reset-voltage threshold levels and reset outputs. The MAX690A/MAX802L/MAX805L generate a reset pulse when the supply voltage drops below 4.65V, and the MAX692A/MAX802M generate a reset below 4.40V. The MAX802L/MAX802M guarantee power-fail accuracies to ±2%. The MAX805L is the same as the MAX690A except that RESET is provided instead of active-low RESET.

All parts are available in 8-pin DIP and SO packages. The MAX690A/MAX802L are pin compatible with the MAX690 and MAX694. The MAX692A/MAX802M are pin compatible with the MAX692.

Applications

* Battery-Powered Computers/Controllers * Critical µP Monitoring * Intelligent Instruments

* Precision Supply Voltage Monitor:

* 4.65V for MAX690A/MAX802L/MAX805L

* 4.40V for MAX692A/MAX802M

* Reset Time Delay: 200ms

* Watchdog Timer: 1.6s Timeout

* Battery-Backup Power Switching

* 200µA Quiescent Supply Current

* 50nA Quiescent Supply Current in Battery-Backup Mode

* Voltage Monitor for Power-Fail or Low-Battery Warning

* Power-Fail Accuracy Guaranteed to ±2% (MAX802L/M)

* Guaranteed Active-Low RESET Assertion to VCC = 1V

* 8-Pin SO and DIP Packages