MAX31785 Datasheet, PDF (1/48 Pages) Maxim Integrated Products – 6-Channel Intelligent Fan Controller

19-5703; Rev 0; 12/10
6-Channel Intelligent Fan Controller
General Description
The MAX31785 is a closed-loop multichannel fan con-
troller. 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 exter-
nal 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.
Applications
Network Switches/Routers
Base Stations
Servers
Smart Grid Network Systems
Industrial Controls
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX31785ETL+
-40NC to +85NC 40 TQFN-EP*
MAX31785ETL+T -40NC to +85NC 40 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
Features
S 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
S 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
S Available 6-Channel ADC to Measure Remote
Voltages
S PMBus™-Compliant Command Interface
S I²C/SMBus™-Compatible Serial Bus with Bus
Timeout Function
S On-Board Nonvolatile Fault Logging and Default
Configuration Setting
S No External Clocking Required
S +3.3V Supply Voltage
PMBus is a trademark of SMIF, Inc.
SMBus is a trademark of Intel Corp.
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, go to: www.maxim-ic.com/errata.
________________________________________________________________ Maxim Integrated Products   1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.