Maxim Integrated MAX691EWE+T Microprocessor Supervisory Circuit

The MAX691EWE+T from Maxim Integrated is a highly integrated microprocessor (µP) supervisory circuit designed to monitor power supplies and microprocessor activity in digital systems. It provides excellent circuit reliability and low cost by eliminating external components and adjustments when used in battery-powered applications. This supervisory circuit ensures that the µP starts up in a known state and operates correctly during power fluctuations or failures.

This device features a combination of functions that make it ideal for microprocessor systems, including a reset output during power-up, power-down, and brownout conditions. The reset signal remains asserted until the supply voltage reaches the reset threshold and maintains it for a minimum of 200ms after VCC has risen above the reset threshold, ensuring a proper system reset. The MAX691EWE+T also features a 1.25V threshold detector for power-fail warning, low battery detection, or to monitor a power supply other than +5V.

The MAX691EWE+T includes a backup battery switchover function that allows the device to switch to a backup battery automatically when a power failure occurs, without any glitch in the supply to the µP. This feature makes it particularly useful for portable and battery-powered equipment. Additionally, the chip includes a watchdog timer that periodically checks for system malfunctions. If the µP does not provide a valid watchdog signal within the preset timeout period, the MAX691EWE+T initiates a system reset, ensuring the system remains operational even in the event of a software hang-up.

Constructed in a 16-pin SOIC package, the MAX691EWE+T operates over a wide temperature range, making it suitable for use in a variety of environments. Its low supply current of 40µA (typical) makes it an energy-efficient choice for portable applications. The device's versatility and robust feature set make it an excellent choice for managing power supplies and ensuring the reliable operation of microprocessor systems in a range of applications.