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