Analog Devices Inc./Maxim Integrated MAX6821TUK+T

Overview

MAX6821TUK+T from Maxim Integrated is a low-voltage microprocessor supervisory IC in 5-pin SOT23 package, featuring push-pull active-low RESET output, 3.08V reset threshold, 140ms minimum reset timeout, 1.6s watchdog timeout, and debounced manual reset input. It monitors VCC for brownout detection and asserts reset during power-up, power-down, or software faults in embedded controllers and portable equipment.

For engineers reviewing the MAX6821TUK+T datasheet, MAX6821TUK+T pinout, MAX6821TUK+T application, or MAX6821TUK+T equivalent, this device serves as a precision voltage monitor with integrated watchdog and manual reset - critical for reliable µP startup and fault recovery in battery-powered and industrial systems.

Technical Context

The MAX6821TUK+T implements a precision bandgap-based voltage reference to detect VCC falling below 3.08V ±1.5% over –40°C to +125°C, with 60ppm/°C temperature coefficient and 2×VTH hysteresis. Its internal reset timer guarantees ≥140ms assertion after VCC recovery, while the watchdog circuit triggers reset if WDI remains static beyond 1.6s (min 1.12s, max 2.4s).

It features dual-reset outputs: active-low push-pull RESET and active-high push-pull RESET, both guaranteed functional down to VCC = +1.0V. The MR input includes a 50kΩ internal pullup and rejects <100ns glitches, enabling direct switch connection without external debounce.

Key Specifications

Pinout & Package

MAX6821TUK+T is housed in a RoHS-compliant 5-pin SOT23-5 package (outline U5-1), measuring 2.9mm × 1.6mm × 1.1mm, suitable for high-density PCB layouts in space-constrained applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6822TUK+T, MAX6821TUK+T provides direct-drive reset without external pullup but lacks bus-sharing flexibility; versus TPS3808G30DBVR, it adds manual reset and tighter threshold tolerance at higher supply current - making it optimal for field-serviceable embedded controllers requiring deterministic 3.08V brownout response.

Availability

MAX6821TUK+T is available at Aetrix Electronics and suitable for set-top boxes, portable/battery-powered equipment, and embedded controllers requiring stable component supply across automotive-grade temperature ranges (–40°C to +125°C).

Supply support for MAX6821TUK+T 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 is a semiconductor company specializing in analog and mixed-signal ICs for power management, sensing, and interface applications.

The MAX6821 series belongs to Maxim's µP supervisory product line, designed specifically for reliable power-on reset, brownout protection, and software fault recovery in resource-constrained embedded systems.

FAQ

What is the exact reset threshold voltage of the MAX6821TUK+T and how tightly is it specified?

The MAX6821TUK+T has a factory-trimmed reset threshold of 3.08V with ±1.5% tolerance over the full –40°C to +125°C operating range. This value is guaranteed in production testing and includes a 2×VTH hysteresis to prevent chatter near the trip point. The 3.08V threshold aligns precisely with 3.3V supply rails, allowing robust brownout detection while maintaining sufficient noise margin.

Does the MAX6821TUK+T require external components to operate, and what happens if the MR pin is left unconnected?

No, the MAX6821TUK+T requires no external components - all timing, reset generation, and pullup functions are integrated. If the MR pin is left unconnected, its internal 50kΩ pullup resistor holds it at VCC, disabling manual reset. This configuration is safe and functional; the device operates solely on VCC monitoring and watchdog supervision without any risk of unintended reset assertion.

How does the watchdog timer in the MAX6821TUK+T respond to WDI signal transitions, and what is the minimum pulse width it detects?

The MAX6821TUK+T watchdog timer clears on any rising or falling edge at the WDI pin and times out only if WDI remains static for >1.12s (min). It detects pulses as narrow as 50ns, enabling reliable software supervision even in high-speed code paths. The 1.6s nominal timeout provides ample margin for complex initialization sequences while preventing false triggers from transient noise.

Can the MAX6821TUK+T maintain valid reset output when VCC drops below 1.8V, and down to what voltage does it guarantee operation?

Yes - the MAX6821TUK+T guarantees correct RESET output state down to VCC = +1.0V, verified across –40°C to +125°C. This ensures deterministic behavior during deep brownout or battery exhaustion, where many competing supervisors fail to assert reset reliably. At VCC = +1.2V, RESET remains fully functional with VOL ≤ 0.3V and VOH ≥ 0.8×VCC, preserving µP reset integrity.

What package type and RoHS status does the MAX6821TUK+T use, and is it compatible with standard SOT23-5 footprints?

The MAX6821TUK+T uses a 5-pin SOT23-5 package (outline U5-1) with lead(Pb)-free construction indicated by the "+T" suffix. It is fully compatible with industry-standard SOT23-5 land patterns (e.g., IPC-7351B SOICN50P190X130-5N), measuring 2.9mm × 1.6mm × 1.1mm. The "+" denotes RoHS compliance per Maxim's packaging standards, and the footprint matches common reflow and inspection tooling.