Analog Devices Inc./Maxim Integrated MAX6821LUK

Overview

MAX6821LUK from Maxim Integrated is a low-voltage microprocessor supervisory IC in 5-pin SOT23 package, combining voltage monitoring (4.63V threshold), 140ms minimum reset timeout, 1.6s watchdog timer, and debounced manual reset input. It asserts active-low push-pull RESET during VCC brownout, power-up, or MR assertion, and guarantees valid reset output down to VCC = +1.0V for reliable embedded controller startup in portable equipment.

For engineers reviewing the MAX6821LUK datasheet, MAX6821LUK pinout, MAX6821LUK application, or MAX6821LUK equivalent, this device serves as a precision voltage supervisor with integrated watchdog and manual reset-critical for fail-safe µP initialization in battery-powered instrumentation, automotive control modules, and industrial edge nodes where supply stability and code execution integrity are non-negotiable.

Technical Context

The MAX6821LUK implements a dedicated analog voltage comparator with 60ppm/°C temperature coefficient and 2×VTH hysteresis to detect VCC falling below its factory-trimmed 4.63V threshold. Its internal reset timer ensures minimum 140ms assertion after VCC recovery, independent of supply ramp rate.

A separate digital watchdog circuit monitors WDI transitions with 50ns pulse detection sensitivity and clears on any rising/falling edge; if no transition occurs within 1.6s (min), it triggers reset for the full tRP duration. MR input features internal 50kΩ pullup and 100ns glitch rejection, enabling direct switch connection without external RC.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, surface-mount, lead-free compatible (UK-T suffix), footprint per JEDEC MO-178AB.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervisory applications.

Compared with MAX6821LUK, MAX6326LUR29 offers simpler supervision without watchdog or MR, while TPS3808G18DBVR targets lower-voltage rails with tunable timeout but removes manual reset-making MAX6821LUK uniquely suited for 5V systems requiring integrated watchdog, MR, and precise 4.63V threshold in minimal footprint.

Availability

MAX6821LUK is available at Aetrix Electronics and suitable for portable medical monitors, automotive body control modules, industrial PLC I/O modules, smart energy meters, and critical µP monitoring applications requiring stable component supply across extended temperature ranges.

Supply support for MAX6821LUK includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) designs precision analog and mixed-signal ICs for industrial, automotive, communications, and computing markets, emphasizing high reliability and low power.

The MAX6821–MAX6825 product line delivers compact, feature-integrated microprocessor supervisors targeting battery-powered and harsh-environment systems where deterministic reset behavior and watchdog coverage are essential.

FAQ

What is the exact reset threshold voltage for MAX6821LUK?

The MAX6821LUK has a factory-trimmed reset threshold of 4.63V, with tolerance of ±130mV over -40°C to +125°C. This value is confirmed in the Threshold Suffix Guide where "L" corresponds to 4.63V, and electrical characteristics tables specify min/typ/max values of 4.47V/4.63V/4.78V across temperature. The MAX6821LUK maintains this threshold accuracy with 60ppm/°C temperature coefficient.

Does MAX6821LUK include a watchdog timer, and what is its timeout period?

Yes, the MAX6821LUK includes a watchdog timer with a nominal timeout period of 1.6 seconds. Electrical characteristics confirm min/typ/max values of 0.80s/1.60s/2.60s over -40°C to +125°C. The timer clears on any rising or falling edge at the WDI pin and triggers reset if no transition occurs within the timeout window-ensuring robust detection of firmware hangs in safety-critical applications.

What type of RESET output does MAX6821LUK provide, and how is it electrically characterized?

The MAX6821LUK provides an active-low push-pull RESET output. When asserted, it sinks up to 3.2mA at VCC ≥4.75V with VOL ≤0.4V; when deasserted, it sources up to 800µA with VOH ≥0.8×VCC. This eliminates need for external pullup resistors and allows direct interfacing with µP reset inputs requiring active-low drive, unlike open-drain variants such as MAX6822.

How does the manual reset (MR) input function on MAX6821LUK, and what are its key electrical specs?

The MR input on MAX6821LUK is active-low with internal 50kΩ pullup to VCC. It accepts logic-low signals down to 0.3×VCC and recognizes pulses as short as 1µs, with 100ns glitch rejection. When pulled low, it asserts RESET for the full 140ms timeout period after MR returns high-enabling reliable field-service reset using a simple momentary switch to GND without external debounce components.

What is the minimum VCC level at which MAX6821LUK guarantees valid RESET output operation?

The MAX6821LUK guarantees correct RESET output state down to VCC = +1.0V, as explicitly stated in the General Description and confirmed in Absolute Maximum Ratings and Electrical Characteristics. This ensures deterministic reset assertion during severe brownout or battery depletion scenarios where other supervisors may fail-critical for preserving system state in portable and automotive applications.