General Description
The MAX31785 is a closed-loop multichannel fan controller. Automatic closed-loop fan control saves system power by operating the fans at the lowest possible speeds. Added benefits of slower fan speeds include lower audible noise, longer fan life, and reduced system maintenance. Based on a user-programmable lookup table (LUT), the device automatically adjusts the speeds of the six independent fans based on one or more of the 11 available temperature sensors. Alternately, an external host can manually command the fan speeds and the device automatically adjusts the fan speeds. The device contains a fan-health-diagnostic function to help users predict impending fan failures. The device can also monitor up to six remote voltages.

FEATUREs
♦ Six Independent Channels of Fan Control
   Supports 3-Wire and 4-Wire Fans
   Automatic Closed-Loop Fan Speed Control
   RPM- or PWM-Based Control
   Optional Manual Mode Control
   Fast and Slow PWM Frequency Options
   Staggered Fan Spin-Up Eases Power-Supply
   Stress
   Dual Tachometer (12-Fan Support)
   Fan-Fault Detection
   Fan-Health Status Meter
   Nonvolatile Fan Operating Run Time Meter
♦ Supports Up to 11 Temperature Sensors
   Up to Six External Thermal Diodes with
   Automatic Series Resistance Cancellation
   One Internal Temperature Sensor
   Up to Four I2C Digital Temperature Sensors
   Fault Detection on All Temperature Sensors
♦ Available 6-Channel ADC to Measure Remote Voltages
♦ PMBus™-Compliant Command Interface
♦ I2C/SMBus-Compatible Serial Bus with Bus Timeout Function
♦ On-Board Nonvolatile Fault Logging and Default Configuration Setting
♦ No External Clocking Required
♦ +3.3V Supply Voltage

APPLICATIONs
  Network Switches/Routers
  Base Stations
  Servers
  Smart Grid Network Systems
  Industrial Controls