Features and Benefits

  • Two Thermal-Diode Inputs
  • Up to 25kHz PWM Output Frequency
  • Three Selectable SMBus Addresses
  • Local Temperature Sensor
  • 1°C Remote Temperature Accuracy
  • Two PWM Outputs for Fan Drive (Open Drain; Can be Pulled Up to +13.5V)
  • Programmable Fan-Control Characteristics
  • Automatic Fan Spin-Up Ensures Fan Start
  • Controlled Rate-of-Change Ensures Unobtrusive Fan-Speed Adjustments
  • ±3% Fan-Speed Measurement Accuracy
  • Temperature Monitoring Begins at POR for Fail-Safe System Protection
  • Active-Low OT and Active-Low THERM Outputs for Throttling or Shutdown
  • Measures Temperatures Up to +150°C
  • MAX6639F is Optimized for n = 1.021 for Penryn Compatibility

Product Details

The MAX6639 monitors its own temperature and one external diode-connected transistor or the temperatures of two external diode-connected transistors, typically available in CPUs, FPGAs, or GPUs. The 2-wire serial interface accepts standard System Management Bus (SMBus) write byte, read byte, send byte, and receive byte commands to read the temperature data and program the alarm thresholds. Temperature data can be read at any time over the SMBus, and three programmable alarm outputs can be used to generate interrupts, throttle signals, or overtemperature shutdown signals.

The temperature data is also used by the internal dual-PWM fan-speed controller to adjust the speed of up to two cooling fans, thereby minimizing noise when the system is running cool, but providing maximum cooling when power dissipation increases. Speed control is accomplished by tachometer feedback from the fan, so that the speed of the fan is controlled, not just the PWM duty cycle. Accuracy of speed measurement is ±4%.

The MAX6639 is available in 16-pin QSOP and 16-pin thin QFN 5mm x 5mm packages. It operates from 3.0V to 3.6V and consumes just 500µA of supply current.


  • Desktop Computers
  • Networking Equipment
  • Notebook Computers
  • Projectors
  • Servers

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.

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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.