Analog Devices Inc./Maxim Integrated MAX6821SUK

Overview

MAX6821SUK from Maxim Integrated is a low-voltage microprocessor supervisory IC in SOT23-5 package, integrating voltage monitoring (4.63V threshold), 140ms minimum reset timeout, 1.6s watchdog timer, manual reset input, and push-pull active-low RESET output. It ensures reliable µP startup and brownout recovery in embedded controllers and portable equipment operating down to VCC = +1.0V.

For engineers reviewing the MAX6821SUK datasheet, MAX6821SUK pinout, MAX6821SUK application, or MAX6821SUK equivalent, this device serves as a precision reset supervisor with guaranteed reset validity at ultra-low supply voltages, immunity to short VCC transients, and no external components required.

Technical Context

The MAX6821SUK implements a dedicated reset generator with hysteresis-based voltage detection and an independent watchdog timer that clears on WDI edge transitions. Its internal 50kΩ MR pullup enables direct switch interfacing without external biasing.

Reset assertion is triggered by VCC falling below 4.63V (±3% over -40°C to +125°C), MR low, or watchdog timeout; RESET remains asserted for ≥140ms after recovery. The push-pull output drives low to ≤0.4V at 3.2mA (VCC ≥4.75V) and high to ≥0.8×VCC at 800µA.

Key Specifications

Pinout & Package

MAX6821SUK is housed in a 5-pin SOT23-5 package (JEDEC MO-178AA), footprint-compatible with industry-standard 5-lead SOT-23 layouts and suitable for high-density PCB designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6821SUK, MAX6326LUR29 sacrifices watchdog capability for lower threshold and open-drain flexibility, while TPS3808G33DBVR trades manual reset and precise 4.63V monitoring for tighter 3.3V tolerance and TI-specific support infrastructure.

Availability

MAX6821SUK is available at Aetrix Electronics and suitable for industrial PLC I/O cards, automotive body control modules, and portable medical monitors requiring stable component supply, long-term lifecycle assurance, and guaranteed parametric compliance.

Supply support for MAX6821SUK 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and computing applications.

The MAX6821–MAX6825 family was designed specifically for space-constrained, low-voltage microprocessor systems needing integrated reset supervision, manual reset, and watchdog protection - all in a minimal 5-pin SOT23 footprint.

FAQ

What is the exact reset threshold voltage for MAX6821SUK?

The MAX6821SUK has a factory-trimmed reset threshold of 4.63V, with ±3% tolerance over the full operating temperature range (-40°C to +125°C). This value is confirmed in the Threshold Suffix Guide where "L" denotes 4.63V, and the Electrical Characteristics table specifies MIN/MAX bounds of 4.47V/4.78V at -40°C to +125°C. The MAX6821SUK uses this precise threshold to supervise +5V rails in mission-critical applications.

Does MAX6821SUK include a watchdog timer, and what is its timeout period?

Yes, the MAX6821SUK includes a watchdog timer with a nominal timeout period of 1.6 seconds. The Electrical Characteristics table lists tWD as 0.80s (min) to 2.60s (max) over -40°C to +125°C, with typical behavior centered at 1.6s. The timer clears on any rising or falling edge at the WDI pin, enabling flexible software integration. This feature is explicitly enabled in the Selector Guide for MAX6821SUK.

What type of RESET output does MAX6821SUK provide, and how is it electrically characterized?

The MAX6821SUK provides an active-low push-pull RESET output. Per the Electrical Characteristics table, VOL is guaranteed ≤0.4V at ISINK = 3.2mA (VCC ≥4.75V), and VOH is ≥0.8×VCC at ISOURCE = 800µA (VCC ≥4.75V). This eliminates the need for an external pullup resistor and ensures clean, rail-to-rail reset signaling compatible with standard µP reset inputs.

Can MAX6821SUK operate reliably at very low supply voltages?

Yes, the MAX6821SUK guarantees correct RESET output state down to VCC = +1.0V, as stated in the General Description and confirmed in the Absolute Maximum Ratings and Electrical Characteristics sections. This allows continued supervision during deep brownout events where other supervisors lose functionality - a key design requirement validated across the full -40°C to +125°C temperature range.

Is there an internal pullup on the MR pin of MAX6821SUK, and what is its value?

Yes, the MAX6821SUK includes an internal 50kΩ pullup resistor on the MR pin, as documented in the Pin Description section and Applications Information. This allows direct connection of a momentary switch from MR to GND without external components. The Electrical Characteristics table confirms MR pullup resistance as 25kΩ (min) to 75kΩ (max), with 50kΩ being the typical value - enabling robust manual reset functionality in compact designs.