Low-Cost Microprocessor Supervisory Circuits with Battery Backup

The MAX703/MAX704 microprocessor (µP) supervisory circuits reduce the complexity and number of components required for power-supply monitoring and battery control functions in µP systems. These devices significantly improve system reliability and accuracy compared to that obtained with separate ICs or discrete components.

The MAX703/MAX704 are available in 8-pin DIP and SO packages and provide four functions:

* An active-low reset during power-up, power-down, and brownout conditions.

* Battery-backup switching for CMOS RAM, CMOS µPs, or other low-power logic circuitry.

* A 1.25V threshold detector for power-fail warning, low-battery detection, or for monitoring a power supply other than +5V.

* An active-low manual reset input.

The MAX703 and MAX704 differ only in their supply-voltage monitor levels. The MAX703 generates a reset when the supply drops below 4.65V, while the MAX704 generates a reset below 4.40V.Applications

* Computers * Controllers * Critical µP Power Monitoring * Intelligent Instruments

* Battery-Backup Power Switching

* Precision Supply-Voltage Monitor

* 4.65V (MAX703)

* 4.40V (MAX704)

* 200ms Reset Pulse Width

* Debounced TTL/CMOS-Compatible Manual Reset Input

* 200µA Quiescent Current

* 50nA Quiescent Current in Battery-Backup Mode

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

* 8-Pin DIP and SO Packages

* Guaranteed RESET-bar Assertion to VCC = 1V