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 asserts a single active-low open-drain RESET output when any monitored supply falls below its threshold, with 140ms minimum timeout and guaranteed operation down to IN1 or IN2 = 1V. Used in telecom and industrial embedded systems for reliable power-up/power-down sequencing.

For engineers reviewing the MAX6339BUT+ datasheet, MAX6339BUT+ pinout, MAX6339BUT+ application, or MAX6339BUT+ equivalent, key selection criteria include factory-trimmed −5% thresholds for three fixed rails, adjustable fourth input, 55µA quiescent current, SOT23-6 package constraints, and reset validity under brownout conditions where IN1/IN2 ≥ 1V.

Technical Context

The MAX6339BUT+ integrates four independent voltage comparators with a shared 1.23V bandgap reference and internal resistor-divider networks for fixed thresholds. Each comparator features 0.3% hysteresis to reject noise without compromising accuracy at nominal voltages.

It operates from IN2 (3.3V supply), powers all internal circuitry, and provides an open-drain RESET output pulled weakly (10µA) to IN2. The device remains functional and asserts valid RESET as long as either IN1 or IN2 exceeds 1V - critical for brownout detection during partial supply collapse.

Key Specifications

Pinout & Package

MAX6339BUT+ is housed in a 6-pin SOT23-6 package (JEDEC MO-178AA), footprint-compatible with industry-standard 2.9mm × 1.6mm × 1.1mm outline. Pin 1 is marked with a dot; top-side marking is "AAJV".

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6340BUT+, MAX6339BUT+ omits watchdog functionality to reduce complexity and cost while retaining identical quad monitoring performance; versus TPS3307-33DGNR, it adds a fourth adjustable input and tighter −5% tolerance on primary rails - making it superior for 4-rail telecom and industrial systems requiring design flexibility.

Availability

MAX6339BUT+ is available at Aetrix Electronics and suitable for telecommunications infrastructure, industrial PLC controllers, and high-end network printers requiring stable component supply with guaranteed long-term availability and traceable sourcing.

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 demanding industrial, communications, and computing applications.

The MAX6339 series delivers compact, low-power quad voltage supervision for multi-supply systems - targeting space-constrained telecom, storage, and embedded control platforms where reliability and rail count justify integrated monitoring.

FAQ

What is the exact threshold voltage for the +2.5V input on MAX6339BUT+?

The +2.5V input on MAX6339BUT+ is specified at −10% tolerance per the Selector Guide footnote †, yielding a threshold range of 2.13V (min) to 2.25V (max). This is confirmed in the Electrical Characteristics table under "+2.5V (−10%) threshold" and applies specifically to the MAX6339BUT+ variant with top-mark "AAJV". The MAX6339BUT+ does not use the −5% option for this rail.

Can MAX6339BUT+ monitor a −12V supply?

MAX6339BUT+ does not natively support −12V monitoring. Its IN4 pin is configured for user-adjustable positive rails referenced to 1.23V. To monitor −12V, an external resistor-divider must scale the negative voltage to match the −5V internal threshold option - but MAX6339BUT+ is not configured for −5V on IN4 (per Selector Guide, IN4 = Adj*). Therefore, −12V monitoring requires a different variant (e.g., MAX6339NUT) or external signal conditioning.

Is the RESET output of MAX6339BUT+ compatible with 5V logic despite being powered from 3.3V?

Yes. The RESET output is open-drain with a weak internal 10µA pullup to IN2 (3.3V), but it can be externally pulled up to any voltage from 0V to +5.5V. When interfacing with 5V logic, an external pullup resistor to +5V overdrives the internal pullup without reverse current flow - a capability explicitly documented in the Applications Information section of the MAX6339BUT+ datasheet.

What happens to RESET if IN2 drops to 1.2V while IN1 remains at 4.8V?

RESET remains asserted (low) as long as either IN1 or IN2 is ≥1V. Since IN2 = 1.2V satisfies this condition, the MAX6339BUT+ continues to operate and holds RESET low until all inputs exceed their thresholds and the 140ms timeout expires. This behavior is guaranteed per the "RESET Valid to IN1 = 1V or IN2 = 1V" specification and is critical for brownout resilience.

Does MAX6339BUT+ require external capacitors for stable operation?

No external capacitors are required for basic operation. The MAX6339BUT+ functions correctly with direct connections to monitored rails. However, a 0.1µF bypass capacitor from IN2 to GND is recommended in electrically noisy environments to improve immunity to fast transients - as noted in the Power-Supply Bypassing section of the datasheet. IN1, IN3, and IN4 may also benefit from added capacitance if transient rejection beyond the built-in 0.3% hysteresis is needed.