Features and Benefits

  • Simple, Automatic Fan-Speed Control
  • Internal and External Temperature Sensing
  • Detect Fan Failure Through Locked-Rotor Output, Tachometer Output, or Fan-Supply Current Sensing
  • Multiple, 1.6% Output Duty-Cycle Steps for Low Audibility of Fan-Speed Changes
  • Pin-Selectable or Factory-Selectable Low-Temperature Fan Threshold
  • Pin-Selectable or Factory-Selectable High-Temperature Fan Threshold
  • Spin-Up Time Ensures Fan Start
  • Fan-Start Delay Minimizes Power-Supply Load at Power-Up
  • 32Hz PWM Output
  • Controlled Duty-Cycle Rate-of-Change Ensures Good Acoustic Performance
  • 2°C Temperature-Measurement Accuracy
  • FULLSPD/FULLSPD Input Sets PWM to 100%
  • Pin-Selectable Active-Low OT Output Threshold
  • 16-Pin QSOP and 10-Pin µMAX Packages

Product Details

The MAX6643/MAX6644/MAX6645 monitor temperature and automatically adjust fan speed to ensure optimum cooling while minimizing acoustic noise from the fan. Each device measures two temperature locations.

The MAX6643/MAX6644/MAX6645 generate a PWM waveform that drives an external power transistor, which in turn modulates the fan's power supply. The MAX6643/MAX6644/MAX6645 monitor temperature and adjust the duty cycle of the PWM output waveform to control the fan's speed according to the cooling needs of the system. The MAX6643 monitors its own die temperature and an optional external transistor's temperature, while the MAX6644 and MAX6645 each monitor the temperatures of one or two external diode-connected transistors.

The MAX6643 and MAX6644 have nine selectable trip temperatures (in 5°C increments). The MAX6645 is factory programmed and is not pin selectable.

All versions include an overtemperature output (active-low OT). Active-low OT can be used for warning or system shutdown. The MAX6643 also features a FULLSPD input that forces the PWM duty cycle to 100%. The MAX6643/MAX6644/MAX6645 also feature a active-low FANFAIL output that indicates a failed fan. See the Selector Guide in the full data sheet for a complete list of each device's functions.

The MAX6643 and MAX6644 are available in a small 16-pin QSOP package and the MAX6645 is available in a 10-pin µMAX® package. All versions operate from 3.0V to 5.5V supply voltages and consume 500µA (typ) supply current.


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

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Product Recommendations

MAX6644 Companion Parts

Recommended Related Parts

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

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(*)The 1Ku list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


Lead Times

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