Fan Controller and Remote Temperature Sensor with SMBus Serial Interface

Industry First - Temperature Sensor with PWM and Linear Fan Control

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The MAX1669 fan controller includes a precise digital thermometer that reports the temperature of a remote sensor. The remote sensor is a diode-connected transistor-typically a low-cost, easily mounted 2N3906 PNP type-replacing conventional thermistors or thermocouples. Remote accuracy is ±3°C for transistors from multiple manufacturers, with no calibration needed. The MAX1669 has an independent fan controller with a low-current logic output requiring external power components to interface to a DC brushless fan. The fan controller has two modes of operation: a low-frequency (20Hz to 160Hz) PWM mode intended for driving the fan motor, or a high-impedance DAC output that generates a variable DC control voltage. In PWM mode, the FAN frequency can be synchronized to an external clock.

Other key features include general-purpose inputs/outputs (GPIOs) for fan presence detection and a thermostat output intended as a fan override signal in case the host system loses the ability to communicate. The internal ADC has a wide input voltage range and gives overrange readings when too large an input voltage is applied. Other error-checking includes temperature out-of-range indication and diode open/short faults.

The MAX1669 is available in a space-saving 16-pin QSOP package that allows it to fit adjacent to the SLOT1 connector.
MAX1669: Typical Operating Circuit MAX1669: Typical Operating Circuit Enlarge+

Key Features

  • Measures Remote CPU Temperature
  • No Calibration Required
  • 20Hz to 160Hz PWM Output for Fan
  • PWM Frequency Sync Input (260kHz)
  • Flexible Fan Interface: Linear or PWM
  • SMBus 2-Wire Serial Interface
  • Programmable Under/Overtemperature Alarms
  • ALERT-bar Latched Interrupt Output
  • OVERT-bar Thermostat Output
  • Two GPIO Pins
  • Write-Once Configuration Protection
  • Supports SMBus Alert Response
  • ±3°C Temperature Accuracy (-40°C to +125°C, remote)
  • 3µA Standby Supply Current
  • +3V to +5.5V Supply Range
  • Small 16-Pin QSOP Package
  • Remote diode sensor, PWM and linear fan control, dual alarms


  • Computers: Desktop, Workstation, Server
  • Notebook Computers
  • Pentium® CPU Cooling
  • Servers
  • Workstations

Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.
Product Reliability Reports: MAX1669.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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