ADM1031
Intelligent Temperature
Monitor and Dual PWM Fan
Controller
The ADM1031 is an ACPI−compliant, three−channel digital
thermometer and under/overtemperature alarm for use in personal
computers and thermal management systems. Optimized for the
PentiumRIII, the part offers a 1°C higher accuracy, which allows
system designers to safely reduce temperature guard−banding and
increase system performance.
Two PWM fan control outputs control the speed of two cooling fans
by varying output duty cycle. Duty cycle values between 33% and
100% allow smooth control of the fans. The speed of each fan can be
monitored via TACH inputs, which can be reprogrammed as analog
inputs to allow speeds for 2−wire fans to be measured via sense
resistors. The device also detects a stalled fan. A dedicated fan speed
control loop provides control without the intervention of CPU
software. It also ensures that if the CPU or system locks up, each fan
can still be controlled based on temperature measurements, and the fan
speed is adjusted to correct any changes in system temperature. Fan
speed can also be controlled using existing ACPI software.
Two inputs (4 pins) are dedicated to remote temperature−sensing
diodes with an accuracy of ±1°C, and an on−chip temperature sensor
allows ambient temperature to be monitored. The device has a
programmable INT output to indicate error conditions, and a dedicated
FAN_FAULT output to signal fan failure. The THERM pin is a
fail−safe output for overtemperature conditions that can be used to
throttle a CPU clock.
http://onsemi.com
QSOP−16
CASE 492
MARKING DIAGRAM
1
1031A
RQZ
#YYWW
xxx = Specific Device Code
#
= Pb−Free Package
YY = Date Code
WW = Work Week
PIN ASSIGNMENT
Features
• Optimized for Pentium III
♦ Reduced Guard−banding Software
♦ Automatic Fan Speed Control, Independent of CPU
Intervention After Initial Setup
• 0.125°C Resolution on External Temperature Channels
• Control Loop to Minimal Acoustic Noise and Battery
Consumption
• Remote Temperature Measurement Accurate to 1°C
Using Remote Diode (Two Channels)
• Local Sensor with 0.25°C Resolution
• Pulse Width Modulation (PWM) Fan Control for 2 Fans
• Programmable PWM Frequency and PWM Duty Cycle
• Tach Fan Speed Measurement (Two Channels)
• Analog Input to Measure Fan Speed of 2−Wire Fans
(Using Sense Resistor)
• 2−Wire System Management Bus (SMBus) with ARA
Support
PWM_OUT1 1
TACH1/AIN1 2
PWM_OUT2 3
TACH2/AIN2 4
GND 5
VCC 6
THERM 7
FAN_FAULT 8
ADM1031
16 SCL
15 SDA
14 INT(SMBALERT)
13 ADD
12 D2+
11 D2–
10 D1+
9 D1–
• Overtemperature THERM Output Pin for CPU
Throttling
• Programmable INT Output Pin
• Configurable Offsets for Temperature Channels 3.0 V
to 5.5 V Supply Range
• Shutdown Mode to Minimize Power Consumption
• Limit Comparison of All Monitored Values
• This is a Pb−Free Device
Applications
• Notebook PCs, Network Servers, and Personal Computers
• Telecommunications Equipment
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 29 of this data sheet.
© Semiconductor Components Industries, LLC, 2010
1
May, 2010 − Rev. 4
Publication Order Number:
ADM1031/D