Maxim 公司的MAX31785是比环六路智能风扇控制器，支持3线和4线风扇，基于RPM或PWM的控制，可选择快慢PWM频率，支持多达11个温度传感器，PMBus兼容，I2C/SMBus兼容，主要用在网络交换/路由器，基站，服务器，智能电网网络系统和工业控制。本文介绍了MAX31785主要特性，方框图，多个器件连接框图以及典型工作电路图。

 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.

MAX31785主要特性：

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

MAX31785应用：

Network Switches/Routers

Base Stations

Servers

Smart Grid Network Systems

Industrial Controls

图1。MAX31785方框图

图2。多个MAX31785器件连接框图

图3。MAX31785自动风扇控制框图

图4。MAX31785典型工作电路图