MAX6644LBAAEE+

Thermal Management Overview

The MAX6644LBAAEE+ is an automatic PWM fan-speed controller with overtemperature output, operating from a 3.0V to 5.5V supply. It measures temperatures of one or two external diode-connected transistors and adjusts the duty cycle of a 32Hz PWM waveform to control fan speed. The device features pin-selectable high-temperature (THIGH) and low-temperature (TLOW) thresholds in 5°C increments, providing up to nine selectable trip points. It includes an active-low open-drain FANFAIL alarm for detecting fan failure via tachometer, locked-rotor, or current sensing, and an OT output for system shutdown warnings.

Thermal Management Feature Summary

• Automatically adjusts fan speed based on temperature measurements to optimize cooling while minimizing acoustic noise
• Detects fan failure through locked-rotor output, tachometer output, or fan-supply current sensing
• Features multiple 1.6% output duty-cycle steps for low audibility of fan-speed changes
• Includes pin-selectable low-temperature and high-temperature fan thresholds

Thermal Management Applications

• Networking Equipment
• Storage Equipment
• Servers
• Desktop Computers
• Workstations

Thermal Management Procurement Notes

Verify the specific suffix 'LBAAEE+' against the manufacturer's official datasheet to confirm package type, temperature range, and factory settings. Ensure compatibility with the required external power transistor and remote diode-connected sensors. Confirm that the 16-pin QSOP footprint matches the target PCB design. Check for any lead-free or RoHS compliance markings if required by the end application standards.

Thermal Management Selection Notes

Select this component when monitoring external diode-connected transistors rather than internal die temperature. The MAX6644 supports dual remote sensor inputs, unlike the MAX6643 which monitors its own die. Verify that the pin-selectable threshold configuration meets the thermal management requirements. Ensure the 32Hz PWM frequency and duty-cycle step resolution are suitable for the connected fan's operational characteristics.

Thermal Management Part Context

The MAX6644 belongs to the MAX6643/MAX6644/MAX6645 family of automatic PWM fan-speed controllers. While the MAX6643 monitors internal and external temperatures, the MAX6644 focuses on one or two external diode-connected transistors. All devices share similar PWM generation and fan-fail detection capabilities but differ in sensor input configurations and package options.

Thermal Management Replacement Considerations

MAX6643LBAAEE+T

Thermal Management FAQ

How does the MAX6644 detect fan failure?

It detects fan failure by monitoring the fan's speed via tachometer pulses, recognizing a locked-rotor logic signal, or sensing variations in the fan-supply current using an external sense resistor.

What is the function of the FULLSPD input?

The FULLSPD input is not available on the MAX6644; it is a feature of the MAX6643. On the MAX6644, fan speed is controlled automatically based on the measured temperature relative to the THIGH and TLOW thresholds.

Can the MAX6644 monitor its own die temperature?

No, the MAX6644 is designed to measure the temperatures of one or two external diode-connected transistors only. The MAX6643 is the variant in this family that monitors its own die temperature.