Analog Devices Inc./Maxim Integrated MAX6639ATE+

Overview

The MAX6639ATE+ from Maxim Integrated is a 2-channel temperature monitor with dual automatic PWM fan-speed controller, measuring local die temperature and up to two remote diode-connected transistors (e.g., in CPUs/FPGAs/GPUs), featuring ±1°C remote accuracy, 11-bit temperature resolution, and open-drain PWM outputs rated for +13.5V pull-up-used in thermal management of desktops, servers, and networking equipment.

For engineers reviewing the MAX6639ATE+ datasheet, MAX6639ATE+ pinout, MAX6639ATE+ application, or MAX6639ATE+ equivalent, key selection considerations include SMBus address configurability (3 options), tachometer-based closed-loop fan speed control (±3% RPM accuracy), programmable OT/THERM alarm outputs, dual 25kHz PWM drive capability, and operation across –40°C to +125°C ambient with 3.0V–3.6V supply.

Technical Context

The MAX6639ATE+ integrates dual independent thermal-diode measurement channels with internal ADCs, each supporting n-factor compensation (n = 1.008 for MAX6639A variants), and uses tachometer feedback-not just duty cycle-to regulate fan RPM in PWM, manual RPM, or automatic RPM modes. It implements register-locked temperature reads to synchronize main and extended registers for 0.125°C resolution.

Its SMBus interface supports write byte, read byte, send byte, and receive byte protocols with three selectable slave addresses (58h/5Ch/5Eh), timeout protection (58–90ms), and 10–100kHz clock frequency compliance. The device initiates temperature conversion at power-on reset for fail-safe system protection and supports pulse-stretching for accurate tachometer measurement under low-duty-cycle PWM conditions.

Key Specifications

Pinout & Package

The MAX6639ATE+ is housed in a 16-pin thin QFN (5mm × 5mm) package with exposed pad (EP) connected internally to GND for enhanced thermal dissipation. Pin 1 is located at top-left corner adjacent to the marking dot; EP must be soldered to a large PCB copper area.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-channel thermal monitoring and PWM fan control applications.

Compared with MAX6642AATA+ and ADM1032ARMZ-REEL, the MAX6639ATE+ uniquely delivers dual remote + local sensing, dual tachometer-closed-loop PWM outputs, and 0.125°C resolution-making it the only option supporting coordinated cooling for heterogeneous compute platforms with CPU+GPU thermal domains.

Availability

The MAX6639ATE+ is available at Aetrix Electronics and suitable for desktop computers, servers, and networking equipment requiring stable component supply, long-term thermal management continuity, and RoHS-compliant packaging.

Supply support for MAX6639ATE+ 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, sensing, and connectivity applications in industrial, computing, and communications markets.

The MAX6639ATE+ belongs to Maxim's thermal management product line, engineered specifically for intelligent, closed-loop fan control in high-performance computing systems where acoustic performance and thermal safety are co-optimized.

FAQ

What is the maximum remote diode temperature measurable by the MAX6639ATE+?

The MAX6639ATE+ measures remote diode temperatures from 0°C to +150°C, with guaranteed accuracy of ±1°C over 0°C to +145°C. Its internal ADC and diode bias circuitry support this full range without external scaling, making it suitable for high-power CPU and GPU thermal monitoring where junction temperatures exceed 100°C.

Does the MAX6639ATE+ support both local and remote temperature sensing simultaneously?

Yes, the MAX6639ATE+ monitors its own die temperature (local sensor) and up to two external diode-connected transistors concurrently. Channel 1 reads the first remote diode; channel 2 reads either the second remote diode or the local sensor-selected via bit 4 in the global configuration register. This dual-mode flexibility enables use in systems with varying thermal sensor topologies.

Can the MAX6639ATE+ PWM outputs drive fans directly, or do they require external MOSFETs?

The MAX6639ATE+ PWM1 and PWM2 outputs are open-drain and cannot source current-they require external pull-up resistors. While they can interface with 4-wire fans' PWM inputs directly (with appropriate pull-up), driving brushless DC fans typically requires external N-channel MOSFETs or bipolar transistors, as specified in the datasheet's application circuits for PWM1/PWM2 terminal usage.

How does the MAX6639ATE+ ensure accurate tachometer measurements when PWM duty cycle is very low?

The MAX6639ATE+ implements automatic pulse stretching during low-duty-cycle PWM operation to guarantee full tachometer pulse capture per revolution. This feature-enabled by default in PWM mode-extends active PWM periods temporarily so the tachometer input can reliably measure fan RPM even when nominal duty cycles fall below 10%, preventing false FANFAIL assertions.

What SMBus timing parameters must be met for reliable communication with the MAX6639ATE+?

The MAX6639ATE+ complies with standard SMBus timing: clock frequency 10–100kHz, minimum clock low/high periods of 4µs/4.7µs, bus free time ≥4.7µs, and data setup/hold times of 250ns/300ns. Its built-in 58–90ms timeout resets the interface if SCL remains low longer-ensuring robustness against bus lockup in multi-master environments.