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Analog Devices Semiconductor Electronic Components Datasheet

ADT7476 Datasheet

dBCool Remote Thermal Controller and Voltage Monitor

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ADT7476 pdf
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dBCoolRemote Thermal
Controller and Voltage Monitor
ADT7476
FEATURES
Monitors up to 5 voltages
Controls and monitors up to 4 fans
High and low frequency fan drive signal
1 on-chip and 2 remote temperature sensors
Extended temperature measurement range up to 191°C
Automatic fan speed control mode controls system cooling
based on measured temperature
Enhanced acoustic mode dramatically reduces user
perception of changing fan speeds
Thermal protection feature via THERM output
Monitors performance impact of Intel® Pentium™ 4
processor
Thermal control circuit via THERM input
3-wire and 4-wire fan speed measurement
Limit comparison of all monitored values
Meets SMBus 2.0 electrical specifications
GENERAL DESCRIPTION
The ADT7476 dBCool controller is a thermal monitor
and multiple PWM fan controller for noise-sensitive or power-
sensitive applications requiring active system cooling. The
ADT7476 can drive a fan using either a low or high frequency
drive signal, monitor the temperature of up to two remote
sensor diodes plus its own internal temperature, and measure
and control the speed of up to four fans, so they operate at
the lowest possible speed for minimum acoustic noise.
The automatic fan speed control loop optimizes fan speed
for a given temperature. The effectiveness of the system’s
thermal solution can be monitored using the THERM input.
The ADT7476 also provides critical thermal protection to
the system using the bidirectional THERM pin as an output
to prevent system or component overheating.
FUNCTIONAL BLOCK DIAGRAM
ADDR
ADDREN SELECT SCL SDA SMBALERT
VID5
VID4/GPIO4
VID3/GPIO3
VID2/GPIO2
VID1/GPIO1
VID0/GPIO0
GPIO6
PWM1
PWM2
PWM3
TACH1
TACH2
TACH3
TACH4
THERM
VCC
D1+
D1–
D2+
D2–
+5VIN
+12VIN
+2.5VIN
VCCP
PWM
REGISTERS
AND
CONTROLLERS
(HF AND LF)
VCC TO ADT7476
BAND GAP
TEMP. SENSOR
VID/GPIO
REGISTER
AUTOMATIC
FAN SPEED
CONTROL
FAN
SPEED
COUNTER
PERFORMANCE
MONITORING
THERMAL
PROTECTION
INPUT
SIGNAL
CONDITIONING
AND
ANALOG
MULTIPLEXER
SMBus
ADDRESS
SELECTION
SERIAL BUS
INTERFACE
ADT7476
ADDRESS
POINTER
REGISTER
PWM
CONFIGURATION
REGISTERS
INTERRUPT
MASKING
ACOUSTIC
ENHANCEMENT
CONTROL
10-BIT
ADC
BAND GAP
REFERENCE
INTERRUPT
STATUS
REGISTERS
LIMIT
COMPARATORS
VALUE AND
LIMIT
REGISTERS
GND
Figure 1.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2006 Analog Devices, Inc. All rights reserved.


Analog Devices Semiconductor Electronic Components Datasheet

ADT7476 Datasheet

dBCool Remote Thermal Controller and Voltage Monitor

No Preview Available !

ADT7476 pdf
ADT7476
TABLE OF CONTENTS
Features .............................................................................................. 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Table of Contents .............................................................................. 2
Revision History ............................................................................... 3
Specifications..................................................................................... 4
Timing Diagram ........................................................................... 5
Absolute Maximum Ratings............................................................ 6
Thermal Resistance ...................................................................... 6
ESD Caution.................................................................................. 6
Pin Configuration and Function Descriptions............................. 7
Typical Performance Characteristics ............................................. 9
Product Description....................................................................... 11
Feature Comparisons Between ADT7476 and ADT7468..... 11
Recommended Implementation............................................... 12
Serial Bus Interface..................................................................... 13
Write Operations ........................................................................ 15
Read Operations ......................................................................... 16
SMBus Timeout .......................................................................... 16
Virus Protection.......................................................................... 16
Voltage Measurement Input...................................................... 17
Analog-to-Digital Converter .................................................... 17
Input Circuitry............................................................................ 17
Voltage Measurement Registers................................................ 17
Voltage Limit Registers .............................................................. 17
Extended Resolution Registers ................................................. 17
Additional ADC Functions for Voltage Measurements ........ 17
VID Code Monitoring ............................................................... 20
VID Code Input Threshold Voltage......................................... 20
VID Code Change Detect Function ........................................ 20
Programming the GPIOs........................................................... 20
Temperature Measurement Method ........................................ 20
Factors Affecting Diode Accuracy........................................... 22
Additional ADC Functions for Temperature
Measurement .............................................................................. 23
Limits, Status Registers, and Interrupts....................................... 25
Limit Values ................................................................................ 25
Status Registers ........................................................................... 26
THERM Timer ........................................................................... 28
Fan Drive Using PWM Control ............................................... 31
Laying Out 3-Wire Fans ............................................................ 33
Programming TRANGE.................................................................. 36
Programming the Automatic Fan Speed Control Loop ............ 37
Manual Fan Control Overview................................................. 37
THERM Operation in Manual Mode...................................... 37
Automatic Fan Control Overview............................................ 37
Step 1: Hardware Configuration .............................................. 38
Step 2: Configuring the Mux .................................................... 41
Step 3: TMIN Settings for Thermal Calibration Channels ...... 43
Step 4: PWMMIN for Each PWM (Fan) Output ...................... 44
Step 5: PWMMAX for PWM (Fan) Outputs.............................. 45
Step 6: TRANGE for Temperature Channels................................ 46
Step 7: TTHERM for Temperature Channels ............................... 48
Step 8: THYST for Temperature Channels.................................. 50
Fan Presence Detect................................................................... 51
Fan Sync....................................................................................... 52
Standby Mode ............................................................................. 52
XNOR Tree Test Mode .............................................................. 52
Power-On Default ...................................................................... 52
Register Tables ................................................................................ 53
Outline Dimensions ....................................................................... 72
Ordering Guide .......................................................................... 72
Rev. A | Page 2 of 72


Part Number ADT7476
Description dBCool Remote Thermal Controller and Voltage Monitor
Maker Analog Devices
Total Page 30 Pages
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