Analog Devices Inc./Maxim Integrated MAX6821YUK+

Overview

MAX6821YUK+ from Maxim Integrated is a low-voltage microprocessor supervisory circuit in 5-pin SOT23 package, featuring push-pull active-low RESET output, manual reset input (MR), and 1.6s watchdog timer. It monitors +2.19V supply with ±3% threshold accuracy over –40°C to +125°C, asserts reset for ≥140ms after VCC recovery, and guarantees valid reset operation down to VCC = +1.0V - used in portable/battery-powered equipment and critical µP monitoring systems.

For engineers reviewing the MAX6821YUK+ datasheet, MAX6821YUK+ pinout, MAX6821YUK+ application, or MAX6821YUK+ equivalent, this page delivers verified pin functions, exact reset threshold (2.19V), watchdog timeout (1.6s), MR debounce behavior, and real-world substitution guidance for embedded controller and intelligent instrument designs.

Technical Context

The MAX6821YUK+ integrates voltage monitoring, watchdog timer, and manual reset into a single BiCMOS IC. Its reset generator triggers on VCC falling below 2.19V (±3% over temperature), holds RESET low for ≥140ms after VCC rises above threshold, and supports MR assertion with internal 50kΩ pullup and 200ns MR-to-reset delay.

The watchdog circuit monitors WDI transitions with 1.6s nominal timeout (0.8s–2.6s over temperature), clears on any edge or reset assertion, and tolerates WDI leakage ≤10µA when unconnected. RESET output drives low with VOL ≤0.3V at ISINK = 500µA and high with VOH ≥0.8×VCC at ISOURCE = 200µA.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5 (U5-1 outline), footprint per land pattern 21-0057, RoHS-compliant (+ suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6821YUK+, MAX6326YUT+T removes watchdog and MR functionality to reduce cost and complexity, while TPS3808G18DBVR trades MR and push-pull drive for lower IQ and tighter threshold tolerance - making MAX6821YUK+ optimal when integrated watchdog + MR + no-external-component operation is required.

Availability

MAX6821YUK+ is available at Aetrix Electronics and suitable for portable/battery-powered equipment, critical µP monitoring, and intelligent instruments requiring stable component supply across extended temperature ranges.

Supply support for MAX6821YUK+ 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, mixed-signal, and power management ICs for industrial, computing, and communications applications.

The MAX6821YUK+ belongs to the MAX682x family of low-voltage µP supervisors - engineered specifically for reliable power-monitoring and fault-recovery in space-constrained, battery-sensitive embedded systems.

FAQ

What is the exact reset threshold voltage for MAX6821YUK+ and how stable is it over temperature?

The MAX6821YUK+ has a factory-trimmed reset threshold of 2.19V with ±3% accuracy over the full –40°C to +125°C operating range. Its temperature coefficient is 60ppm/°C, resulting in ≤15mV drift across 100°C - verified in the Electrical Characteristics table under VTH for MAX682_Y suffix. This stability ensures consistent brownout detection in automotive and industrial environments where MAX6821YUK+ is deployed.

Does MAX6821YUK+ require external components for basic operation?

No, MAX6821YUK+ operates autonomously with zero external components. It integrates an internal 50kΩ pullup on the MR pin, precision voltage reference, watchdog oscillator, and push-pull RESET driver. The datasheet explicitly states "No External Components" as a key feature, and typical operating circuits show direct connection to VCC, GND, MR switch, and WDI - confirming MAX6821YUK+ needs no capacitors, resistors, or diodes for core supervision functionality.

How does the watchdog timer in MAX6821YUK+ behave when the WDI pin is left unconnected?

When WDI is unconnected, MAX6821YUK+ disables the watchdog function. The internal circuitry services the timer every ~1.4s via a low-high-low pulse, preventing timeout. This behavior is documented in the Applications Information section and confirmed in the Pin Description: "Disable the watchdog function by leaving WDI unconnected." Thus, MAX6821YUK+ operates as a pure voltage supervisor unless WDI is actively driven.

What is the minimum VCC voltage at which MAX6821YUK+ guarantees correct RESET output state?

MAX6821YUK+ guarantees correct RESET output state (i.e., valid logic levels and timing) down to VCC = +1.0V - stated in the General Description and reinforced in Absolute Maximum Ratings. This means RESET remains asserted low with VOL ≤0.3V even as VCC collapses to 1.0V, ensuring µP stays held in reset during deep brownout - a key differentiator versus competitors that specify reset validity only down to VCC = +1.2V or higher.

Can MAX6821YUK+ be used in systems requiring both active-low and active-high reset signals?

MAX6821YUK+ provides only active-low push-pull RESET output (pin 1). It does not offer complementary active-high RESET (pin 3) - that function is present in MAX6823/MAX6824/MAX6825 variants but excluded from MAX6821YUK+. Therefore, MAX6821YUK+ cannot natively drive both polarities; external inversion (e.g., single transistor or gate) would be required to generate active-high reset, adding complexity that defeats the "no external components" advantage of MAX6821YUK+.