Analog Devices Inc./Maxim Integrated MAX6821WUK

Overview

MAX6821WUK from Maxim Integrated is a low-voltage microprocessor supervisory IC in SOT23-5 package, integrating voltage monitoring, watchdog timer, and manual reset input. It monitors +1.67V supply with 140ms minimum reset timeout, asserts push-pull active-low RESET, operates down to VCC = +1.0V, and supports automotive-grade temperature range (–40°C to +125°C) for critical µP power-up/brownout protection.

For engineers reviewing the MAX6821WUK datasheet, MAX6821WUK pinout, MAX6821WUK application, or MAX6821WUK equivalent, this device serves as a single-chip solution for reliable reset generation, code-execution error detection via 1.6s watchdog, and noise-immune manual reset in space-constrained embedded systems.

Technical Context

The MAX6821WUK implements a precision bandgap-based voltage monitor with ±1.5% threshold accuracy over temperature, triggering reset when VCC falls below 1.67V. Its internal watchdog timer detects µP firmware hangs by requiring WDI edge transitions within 1.6s nominal timeout-cleared on any rising/falling edge or reset assertion.

A dedicated MR input features 50kΩ internal pullup and 100ns glitch rejection; reset remains asserted for ≥140ms after MR returns high. The push-pull RESET output guarantees valid logic state down to VCC = +1.0V and sinks up to 3.2mA while maintaining VOL ≤ 0.4V at VCC ≥ 4.75V.

Key Specifications

Pinout & Package

MAX6821WUK is housed in a RoHS-compliant 5-pin SOT23-5 package (2.9mm × 1.6mm × 1.1mm), optimized for high-density PCB layouts and reflow soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6821WUK, MAX6326UR29 removes watchdog and MR capability but offers longer timeout and open-drain flexibility, while TPS3808G16DBVR trades MR and watchdog for lower ICC-making MAX6821WUK optimal when full supervisory feature integration is mandatory.

Availability

MAX6821WUK is available at Aetrix Electronics and suitable for automotive ECUs, portable medical devices, industrial PLC modules, and set-top boxes requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6821WUK 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.

The MAX6821–MAX6825 family was engineered specifically for space-constrained, high-reliability microprocessor supervision-combining voltage monitoring, watchdog, and manual reset in a single 5-pin SOT23 package.

FAQ

What is the exact reset threshold voltage for MAX6821WUK?

The MAX6821WUK has a factory-trimmed reset threshold of 1.67V, specified with ±1.5% tolerance over the full –40°C to +125°C operating range. This value corresponds to the 'W' suffix in the Threshold Suffix Guide and is guaranteed by design-not production tested-per Maxim's datasheet Note 1. The MAX6821WUK uses this precise threshold to supervise +1.8V logic rails during brownout events.

Does MAX6821WUK include a watchdog timer, and what is its timeout period?

Yes, the MAX6821WUK includes a watchdog timer with a nominal timeout period of 1.6 seconds, varying from 0.8s to 2.6s over temperature. The timer clears on any rising or falling edge at the WDI pin, on MR assertion, or during RESET assertion. Unlike some alternatives, the MAX6821WUK watchdog does not require strict high-low-high toggling-it responds to any edge transition, simplifying firmware implementation.

What type of RESET output does MAX6821WUK provide, and how is it electrically characterized?

The MAX6821WUK provides an active-low push-pull RESET output. When asserted, it sinks up to 3.2mA while maintaining VOL ≤ 0.4V at VCC ≥ 4.75V; when deasserted, it sources up to 800µA with VOH ≥ 0.8 × VCC. This eliminates the need for an external pullup resistor and ensures robust drive strength into µP reset pins-even at VCC as low as +1.0V.

Can MAX6821WUK operate reliably during severe supply transients?

Yes, the MAX6821WUK is designed to reject short negative-going VCC transients: a 100mV dip below the 1.67V threshold lasting ≤20µs will not trigger a false reset. This immunity is validated per Maxim's Typical Operating Characteristics graph "Maximum VCC Transient Duration vs. Reset Threshold Overdrive" and makes the MAX6821WUK suitable for automotive and industrial environments with noisy power distribution.

Is manual reset supported on MAX6821WUK, and what are its electrical requirements?

Yes, MAX6821WUK includes an active-low manual reset (MR) input with internal 50kΩ pullup to VCC. It accepts CMOS-compatible logic levels (VIH ≥ 0.7×VCC, VIL ≤ 0.3×VCC), rejects glitches <100ns, and asserts reset for ≥140ms after MR returns high. No external debounce components are needed-simply connect a momentary switch from MR to GND. This MR functionality is confirmed in the Selector Guide and Pin Description sections of the MAX6821WUK datasheet.