Analog Devices Inc./Maxim Integrated MAX6339BUT

Overview

MAX6339BUT from Maxim Integrated is a precision quad voltage supervisory IC that monitors +5.0V (−5%), +3.3V (−5%), +2.5V (−5%), and one user-adjustable input (1.23V internal reference) in multi-rail systems. It delivers a single active-low open-drain RESET output with 140ms minimum timeout, consumes only 55µA supply current, and operates from −40°C to +85°C. It is used in desktop computers and networking equipment for reliable power-on reset and brownout detection.

For engineers reviewing the MAX6339BUT datasheet, MAX6339BUT pinout, MAX6339BUT application, or MAX6339BUT equivalent, key selection criteria include factory-trimmed −5% threshold accuracy per rail, IN2-powered operation, guaranteed RESET validity down to IN1 = 1V or IN2 = 1V, immunity to short transients (<1µs at 50mV overdrive), and SOT23-6 footprint compatibility with space-constrained embedded designs.

Technical Context

The MAX6339BUT integrates four independent precision comparators with a shared 1.23V bandgap reference and internal resistor-divider networks calibrated for fixed −5% thresholds on IN1 (+5.0V), IN2 (+3.3V), and IN3 (+2.5V). Its fourth input (IN4) bypasses internal dividers and accepts externally set thresholds via resistor-divider networks referenced to the 1.23V comparator input.

RESET assertion is controlled by a NOR gate combining all comparator outputs, followed by a 140ms minimum timeout monostable circuit. The open-drain output features a weak 10µA internal pullup to IN2, eliminating need for external pullups in many 3.3V logic interfaces while supporting overdrive to 0–5.5V logic supplies without reverse current flow.

Key Specifications

Pinout & Package

MAX6339BUT is housed in a 6-pin SOT23-6 package (2.9mm × 1.6mm × 1.1mm height), optimized for high-density PCB layouts and reflow-compatible assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6339BUT, MAX6340BUT offers stricter −10% thresholds but sacrifices compatibility with −5% system specs, while TPS3808G33 lacks the fourth rail and adjustable capability - both require design changes to replace MAX6339BUT in quad-supply applications.

Availability

MAX6339BUT is available at Aetrix Electronics and suitable for desktop computers, networking equipment, high-end printers, and data storage equipment requiring stable component supply, long-term lifecycle support, and guaranteed −5% threshold accuracy across temperature.

Supply support for MAX6339BUT 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 power management, sensing, and interface applications in industrial, computing, and communications markets.

The MAX6339 family delivers compact, low-power quad voltage supervision for multi-rail systems where space, accuracy, and reliability are critical - targeting x86/ARM platforms, telecom infrastructure, and high-end peripherals.

FAQ

What is the exact reset threshold voltage for each monitored rail in MAX6339BUT?

The MAX6339BUT has factory-trimmed −5% thresholds: IN1 trips at ≤4.75V (for +5.0V nominal), IN2 at ≤3.15V (for +3.3V), and IN3 at ≤2.38V (for +2.5V). IN4 uses a 1.23V internal reference, requiring external resistors to set custom thresholds. These values are guaranteed over −40°C to +85°C with ±60ppm/°C drift.

Can MAX6339BUT monitor a −5V supply?

No - MAX6339BUT does not support −5V monitoring. Its IN4 input is user-adjustable but configured for positive voltages only (1.23V reference). For −5V supervision, select MAX6339MUT or MAX6339NUT variants, which include dedicated −5V fixed-threshold options. Using MAX6339BUT for negative rails would require external level-shifting circuitry not supported by its architecture.

Is an external pullup resistor required for the RESET output of MAX6339BUT?

No external pullup is required when interfacing with 3.3V logic, as MAX6339BUT provides a 10µA internal pullup to IN2. If driving logic with a different supply (e.g., 5V or 1.8V), an external pullup to that voltage is needed - the internal pullup is automatically disabled during overdrive, preventing reverse current into IN2.

How does MAX6339BUT handle short-duration supply transients?

MAX6339BUT rejects transients shorter than ~1µs when overdriven by ≥50mV beyond threshold, as confirmed by glitch-immunity characterization (MAX6339toc04). This is achieved through comparator hysteresis (0.3%) and internal filtering - ensuring robust operation in electrically noisy environments like switch-mode power supply outputs.

What happens to the RESET output when IN2 drops below 1V in MAX6339BUT?

When IN2 falls below 1V, the RESET output becomes invalid and may float or behave unpredictably, as MAX6339BUT's internal circuitry requires ≥1V on either IN1 or IN2 to guarantee correct RESET state. Below this, the device loses power and cannot assert or maintain reset - system-level brownout protection must ensure IN1 or IN2 stays ≥1V until safe shutdown completes.