Fan-Speed Regulators and Monitors with SMBus/I²C-Compatible Interface

Controls and Monitors Fan Speed for High-Performance Thermal Management

Please check latest availability status for a specific part variant.


The MAX6650/MAX6651 fan controllers use an SMBus/I²C-compatible interface to regulate and monitor the speed of 5VDC/12VDC brushless fans with built-in tachometers. They automatically force the fan's tachometer frequency (fan speed) to match a preprogrammed value in the Fan-Speed Register by using an external MOSFET or bipolar transistor to linearly regulate the voltage across the fan. The MAX6650 regulates the speed of a single fan by monitoring its tachometer output. The MAX6651 also regulates the speed of a single fan, but it contains additional tachometer inputs to monitor up to four fans and control them as a single unit when they are used in parallel.

The MAX6650/MAX6651 provide general-purpose input/output (GPIO) pins that serve as digital inputs, digital outputs, or various hardware interfaces. Capable of sinking 10mA, these open-drain inputs/outputs can drive an LED. To add additional hardware control, configure GPIO1 to fully turn on the fan in case of software failure. To generate an interrupt when a fault condition is detected, configure GPIO0 to behave as an active-low alert output. Synchronize multiple devices by setting GPIO2 (MAX6651 only) as an internal clock output or an external clock input.

The MAX6650 is available in a space-saving 10-pin µMAX® package, and the MAX6651 is available in a small 16-pin QSOP package.
MAX6650, MAX6651: Typical Operating Circuit MAX6650, MAX6651: Typical Operating Circuit Enlarge+

Key Features

  • Closed/Open-Loop Fan-Speed Control for 5V/12V Fans
  • 2-Wire SMBus/I²C-Compatible Interface
  • Monitors Tachometer Output
    • Single Tachometer (MAX6650)
    • Up to Four Tachometers (MAX6651)
  • Programmable Alert Output
  • GPIOs
  • Hardware Full-On Override
  • Synchronize Multiple Fans
  • Four Selectable Slave Addresses
  • 3V to 5.5V Supply Voltage
  • Small Packages
    • 10-Pin µMAX (MAX6650)
    • 16-Pin QSOP (MAX6651)


  • Computers: Desktop, Workstation, Server
  • Networking
  • RAID
  • Servers
  • Telecommunications
  • Workstations

See parametric specs for Fan Controllers (20)

Part NumberFan ControlInterfacePackage/PinsBudgetary
See Notes
MAX6650 Linear2-Wire/I2C/SMBus
$2.68 @1k
$2.74 @1k

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.

MAX6651EVCMAXQU: MAX6651 Evaluation Kit/Evaluation System
MAX6651EVKIT: MAX6651 Evaluation Kit/Evaluation System
Product Reliability Reports: MAX6651.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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