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ADT7468ARQ-ADT7468ARQ-REEL
dBCOOL™ Remote Thermal Controller and Voltage Monitor
dBCool™ Remote Thermal
Controller and Voltage Monitor
Rev. 0
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
Series resistance cancellation on the remote channel
Extended temperature measurement range, up to 191°C
Dynamic TMIN control mode optimizes system acoustics
intelligently
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
2-wire, 3-wire, and 4-wire fan speed measurement
Limit comparison of all monitored values
Meets SMBus 2.0 electrical specifications
(fully SMBus 1.1 compliant)
GENERAL DESCRIPTION The ADT7468 dBCOOLTM controller is a thermal monitor and
multiple PWM fan controller for noise-sensitive or power-
sensitive applications requiring active system cooling. The
ADT7468 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 that they operate at
the lowest possible speed for minimum acoustic noise.
The automatic fan speed control loop optimizes fan speed for a
given temperature. A unique dynamic TMIN control mode
enables the system thermals/acoustics to be intelligently
managed. The effectiveness of the system’s thermal solution can
be monitored using the THERM input. The ADT7468 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 SCLSDA
VCC
D1+
D1–
D2+
D2–
+5VIN
PWM1
PWM2
PWM3
TACH1
TACH2
TACH3
TACH4
+12VIN
+2.5VIN
VCCP
VID5
VID4
VID3
VID2
VID1
VID0
THERM
SMBALERT
Figure 1.
TABLE OF CONTENTS Specifications.....................................................................................3
Absolute Maximum Ratings............................................................5
Thermal Characteristics..............................................................5
ESD Caution..................................................................................5
Pin Configuration and Function Descriptions.............................6
Typical Performance Characteristics.............................................8
Product Description.......................................................................10
Comparison between ADT7463 and ADT7468.....................10
How to Set the Functionality of Pin 14...................................11
Recommended Implementation...............................................11
Serial Bus Interface.....................................................................12
Write Operations........................................................................13
Read Operations.........................................................................14
SMBus Timeout..........................................................................14
Voltage Measurement Input......................................................14
Analog-to-Digital Converter....................................................14
Input Circuitry............................................................................15
Voltage Measurement Registers................................................15
Voltage Limit Registers..............................................................15
VID Code Monitoring...............................................................15
VID Code Input Threshold Voltage.........................................15
VID Code Change Detect Function........................................16
Additional ADC Functions for Voltage Measurements........16
Temperature Measurement Method........................................18
Series Resistance Cancellation..................................................19
Factors Affecting Diode Accuracy...........................................19
Additional ADC Functions for Temperature Measurement.21
Limits, Status Registers, and Interrupts.......................................22
Limit Values.................................................................................22
Status Registers...........................................................................23
THERM Timer...........................................................................25
Fan Drive Using PWM Control...............................................28
Laying Out 2-Wire and 3-Wire Fans.......................................30
Operating from 3.3 V Standby..................................................34
XNOR Tree Test Mode..............................................................35
Power-On Default......................................................................35
Programming the Automatic Fan Speed Control Loop............36
Automatic Fan Control Overview............................................36
Step 1: Hardware Configuration..............................................37
Recommended Implementation 1...........................................38
Recommended Implementation 2...........................................39
Step 2: Configuring the MUX...................................................40
Step 3: TMIN Settings for Thermal Calibration Channels.......42
Step 4: PWMMIN for Each PWM (Fan) Output.......................43
Step 5: PWMMAX for PWM (Fan) Outputs..............................43
Step 7: TTHERM for Temperature Channels...............................47
Step 8: THYST for Temperature Channels..................................48
Dynamic TMIN Control Mode...................................................49
Step 9: Operating Points for Temperature Channels.............51
Step 10: High and Low Limits for Temperature Channels...52
Step 11: Monitoring THERM...................................................55
Enhancing System Acoustics....................................................56
Step 12: Ramp Rate for Acoustic Enhancement.....................58
Register Tables................................................................................60
ADT7468 Programming Block Diagram....................................79
Outline Dimensions.......................................................................80
Ordering Guide..........................................................................80
REVISION HISTORY Revision 0: Initial Version
SPECIFICATIONS TA = TMIN to TMAX, VCC = VMIN to VMAX, unless otherwise noted.
All voltages are measured with respect to GND, unless otherwise specified. Typicals are at TA = 25°C and represent most likely parametric
norm. Logic inputs accept input high voltages up to VMAX even when device is operating down to VMIN. Timing specifications are tested at
logic levels of VIL = 0.8 V for a falling edge and VIH = 2.0 V for a rising edge. SMBus timing specifications are guaranteed by design and are
not production tested.
Table 1. SCL
SDAtSU; DATtRtHIGH04499-0-002
Figure 2. Serial Bus Timing Diagram
ABSOLUTE MAXIMUM RATINGS
Table 2. Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL CHARACTERISTICS 24-lead QSOP package:
θJA = 150°C/W
θJC = 39°C/W
ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
