Remote Temperature Switches with Integrated Fan Controller/Driver

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The MAX6668/MAX6670 remote-junction thermal switches with an internal power transistor drive a cooling fan rated for supply voltages up to +12V and 250mA. These devices measure the temperature of an external P-N junction (typically a diode-connected transistor) and turn on the fan power switch when the remote temperature rises above a factory-programmed threshold. Self-contained and requiring no software development, the MAX6668/MAX6670 are simple “drop-in” fan-control solutions for a variety of systems.

The MAX6670 features an open-drain active-low WARN output that goes active when the remote temperature exceeds the factory-programmed fan activation threshold by +15°C. The MAX6670 features an open-drain OT output that goes active when the remote temperature exceeds the factory-programmed threshold by +30°C. The MAX6668/MAX6670 provide a fan-control input, active-low FORCEON, that allows the fan to be driven externally, regardless of temperature.

Available temperature thresholds range from +40°C to +75°C in 5°C increments. Hysteresis is preset to 8°C on the MAX6668 or pin selectable to 4°C, 8°C, or 12°C using a three-level logic input on the MAX6670. Temperature threshold accuracy is ±1°C (typ) and ±2.2°C (max) for remote-junction temperatures from +40°C to +75°C.

The MAX6668/MAX6670 operate from a +3V to +3.6V power supply, and are specified over the automotive temperature range (-40°C to +125°C). The MAX6668 is offered in an 8-pin µMAX package and the MAX6670 is available in a space-saving 10-pin µMAX package.
MAX6668, MAX6670: Typical Operating Circuit MAX6668, MAX6670: Typical Operating Circuit Enlarge+

Key Features

  • +12V, 250mA Integrated Fan Driver
  • No Calibration Required
  • Pin-Selectable 4°C, 8°C, or 12°C Hysteresis (MAX6670)
  • Factory-Programmed Temperature Thresholds from +40°C to +75°C
  • Overtemperature Warning Signals
  • 110µA (typ) Supply Current
  • Space-Saving 8-Pin and 10-Pin µMAX Packages


  • Card Racks
  • Fan Control
  • Laboratory Instruments
  • Network Hubs, Switches, Routers
  • Notebook and Desktop Computers
  • PC Power Supplies
  • Temperature Alarms
Product Reliability Reports: MAX6668.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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