MAX809L Microprocessor Reset Circuit

The MAX809L from Maxim Integrated is a compact, highly efficient microprocessor (µP) supervisory circuit designed to monitor power supplies in digital systems. It provides a significant level of protection to digital systems by ensuring a proper reset is executed during power-up, power-down, or brown-out conditions. This device is particularly well-suited for portable and space-constrained applications due to its small size and low power consumption.

The MAX809L is capable of asserting a reset signal whenever the VCC supply voltage declines below a preset threshold, keeping it asserted until the supply voltage stabilizes above the threshold plus a certain hysteresis margin. This ensures that the microprocessor and associated digital circuitry reset in a predictable manner and start operation from a clean state whenever power is applied or restored after an interruption.

One of the key features of the MAX809L is its ability to provide a reset signal with an active-low RESET output. The reset signal remains active for a minimum of 140ms after VCC has risen above the reset threshold level, ensuring sufficient time for the system to stabilize before coming out of reset. This timing precision is maintained over the full temperature range and does not require any external components, thus simplifying the design and reducing the bill of materials.

The device is available in a variety of surface-mount packages, including the SOT23 and SC70, which are highly favored for space-constrained applications. Its low supply current of 17µA (typical) makes it an excellent choice for battery-powered equipment such as computers, controllers, intelligent instruments, and portable consumer products.

The MAX809L operates over a wide voltage range from 1V to 10V and is designed to support a variety of microprocessor systems with different power requirements. Its robust design ensures reliable operation even under adverse conditions, making it a trusted component in critical applications where system reliability is paramount.