The MAX805SCSA+T from Maxim Integrated is a highly reliable 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 with 5V-powered circuits.

This supervisory circuit ensures that the µP is reset to a known state during power-up, power-down, or brown-out conditions. The MAX805SCSA+T asserts a reset signal whenever the VCC supply voltage declines below a preset threshold, keeping it asserted for at least 140ms after VCC has risen above the reset voltage threshold. This feature is critical for systems where a proper startup sequence is essential for safe and predictable operation.

Additionally, the device integrates a watchdog timer that is periodically triggered by a signal from the µP. If the µP fails to refresh the watchdog circuit within a preset timeout period, the device will assert a reset signal. This ensures that if the µP is stuck due to a software error, the system can recover by resetting the processor and starting the process anew.

The MAX805SCSA+T is available in a 4-pin SOT-143 package, making it suitable for space-constrained applications. Its operating temperature range is from -40°C to +85°C, which allows for use in a wide range of environments and applications. The device also features a low supply current of 17µA, which is beneficial for portable and battery-powered applications where power conservation is crucial.

Key features of the MAX805SCSA+T include:

• Precision monitoring of 5V power supplies
• 140ms min power-on reset pulse width
• Watchdog timer with 1.6s timeout (min)
• Manual reset input
• Low supply current of 17µA (typ)
• Guaranteed reset valid to VCC = 1V
• Operates from -40°C to +85°C

This supervisory circuit is ideal for use in microprocessor systems, computers, controllers, intelligent instruments, and critical µP power monitoring. It enhances system reliability and provides a significant level of protection against power supply anomalies, ensuring that the digital system operates effectively and safely.