Analog Devices ADT7460 User manual

dB COOL™ Remote Thermal
Controller and Fan Controller
ADT7460
Rev. C
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
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registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2005 Analog Devices, Inc. All rights reserved.
FEATURES
Controls and monitors up to 4 fan speeds
1 on-chip and 2 remote temperature sensors
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 and 3-wire fan speed measurement
Limit comparison of all monitored values
Meets SMBus 2.0 electrical specifications (fully
SMBus 1.1-compliant)
APPLICATIONS
Low acoustic noise PCs
Networking and telecommunications equipment
GENERAL DESCRIPTION
The ADT74601dBCOOL controller is a thermal monitor and
multiple PWM fan controller for noise-sensitive applications
requiring active system cooling. It can monitor the temperature
of up to two remote sensor diodes plus its own internal temp-
erature. It can 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
ADT7460 also provides critical thermal protection to the
system by using the bidirectional THERM pin as an output
to prevent system or component overheating.
FUNCTIONAL BLOCK DIAGRAM
03228-001
INPUT
SIGNAL
CONDITIONING
AND
ANALOG
MULTIPLEXER
GND
SERIAL BUS
INTERFACE
SCL SDA
VALUE AND
LIMIT
REGISTERS
LIMIT
COMPARATORS
INTERRUPT
STATUS
REGISTERS
BAND GAP
TEMP SENSOR
V
CC
TO ADT7460
ADDRESS
POINTER
REGISTER
PWM
CONFIGURATION
REGISTERS
INTERRUPT
MASKING
V
CC
D1+
D1–
D2+
D2–
+2.5V
IN
THERMAL
PROTECTION
PERFORMANCE
MONITORING
PWM REGISTERS
AND
CONTROLLERS
PWM1
PWM2
PWM3
ACOUSTIC
ENHANCEMENT
CONTROL
BAND GAP
REFERENCE
10-BIT
ADC
ADT7460
AUTOMATIC
FAN SPEED
CONTROL
DYNAMIC
T
MIN
CONTROL
FAN SPEED
COUNTER
TACH1
TACH2
TACH3
TACH4
THERM
SMBALERT
SMBUS
ADDRESS
SELECTION
ADDR
SELECT ADDR_EN
Figure 1.
1Protected by U.S. Patent Nos. 6,188,189; 6,169,442; 6,097,239; 5,982,221; and 5,867,012. Other patents pending.

ADT7460
Rev. C | Page 2 of 52
TABLE OF CONTENTS
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
Thermal Characteristics .............................................................. 5
ESD Caution.................................................................................. 5
Pin Configuration and Function Descriptions............................. 6
Typical Performance Characteristics ............................................. 7
Product Description......................................................................... 9
Measurement Inputs .................................................................... 9
Sequential Measurement ............................................................. 9
Recommended Implementation................................................. 9
ADT7460 Address Selection ..................................................... 10
Internal Registers of the ADT7460 .......................................... 10
Theory of Operation ...................................................................... 11
Serial Bus Interface..................................................................... 11
Voltage Measurement Input...................................................... 15
Additional ADC Functions for Voltage Measurements........ 17
Temperature Measurement System.......................................... 17
Additional ADC Functions for Temperature Measurement 19
Limits, Status Registers, and Interrupts................................... 20
Status Registers ........................................................................... 21
Handling SMBALERT Interrupts............................................. 22
THERM Timer ........................................................................... 24
Fan Drive Using PWM Control ............................................... 27
Operating from 3.3 V Standby ................................................. 33
XNOR Tree Test Mode .............................................................. 33
Power-On Default ...................................................................... 33
ADT7460 Register Summary........................................................ 34
Outline Dimensions ....................................................................... 51
Ordering Guide .......................................................................... 51
REVISION HISTORY
3/05—Rev. B to Rev. C
Updated Format.................................................................. Universal
Changes to Absolute Maximum Ratings Table..............................5
Changes to ADT7460 Register Map Summary Section .............34
Updated Ordering Guide................................................................51
9/03—Rev. A to Rev. B
Changed XOR Tree Test Mode to XNOR ............................ Universal
Changes to SPECIFICATIONS............................................................. 2
Changes to TPC 7....................................................................................7
6/03—Rev. 0 to Rev. A
Updated ORDERING ............................................................................4
Updated the SERIAL BUS INTERFACE section................................9
Added the To Assign THERM Functionality to a Pin 9 section ....21
Added the THERM as an Input section.............................................21
Renamed the Therm Input section to THERM Timer ....................21
Renumbered the figures after Figure 25.............................................22
Updated Step 1 in the Configuring the Desired THERM Behavior
section........................................................................................................2
Updated the Fan Speed Control section ............................................28
Added the POWER-ON DEFAULT section .....................................29
Updated Table IV ..................................................................................30
Updated Table XVIII ............................................................................38
Updated Table XX .................................................................................40
Updated Table XXXV ...........................................................................46
Updated OUTLINE DIMENSIONS ...................................................49

ADT7460
Rev. C | Page 3 of 52
SPECIFICATIONS
TA= TMIN to TMAX, VCC = VMIN to VMAX, unless otherwise noted.
Table 1.
Parameter1, ,2 3 Min Typ4Max Unit Test Conditions/Comments
POWER SUPPLY
Supply Voltage 3.0 5.0 5.5 V
Supply Current, ICC 3 mA Interface inactive, ADC active
20 µA Standby mode
TEMPERATURE-TO-DIGITAL CONVERTER
Local Sensor Accuracy ±1.5 °C 0°C ≤ TA≤ 70°C
±3 °C −40°C ≤ TA≤ +120°C
Resolution 0.25 °C
Remote Diode Sensor Accuracy ±1.5 °C 0°C ≤ TA≤ 70°C; 0°C ≤ TD≤ 120°C
±2.5 °C 0°C ≤ TA≤ 105°C; 0°C ≤ TD≤ 120°C
±3 °C 0°C ≤ TA≤ 120°C; 0°C ≤ TD≤ 120°C
Resolution 0.25 °C
Remote Sensor Source Current 180 µA High level
11 µA Low level
ANALOG-TO-DIGITAL CONVERTER
(INCLUDING MUX AND ATTENUATORS)
Total Unadjusted Error, TUE ±1.5 %
Differential Nonlinearity, DNL ±1 LSB 8 bits
Power Supply Sensitivity ±0.1 %/V
Conversion Time (Voltage Input) 11.38 13 ms Averaging enabled
Conversion Time (Local Temperature) 12.09 13.50 ms Averaging enabled
Conversion Time (Remote Temperature) 25.59 28 ms Averaging enabled
Total Monitoring Cycle Time 120.17 134.50 ms Averaging enabled (incl. delay5)
13.51 15 ms Averaging disabled
Input Resistance 80 140 200 kΩ
FAN RPM-TO-DIGITAL CONVERTER
Accuracy ±7 % 0°C ≤ TA≤ 70°C
±11 % 0°C ≤ TA≤ 105°C
±13 % −40°C ≤ TA≤ +120°C
Full-Scale Count 65,535
Nominal Input RPM 109 RPM Fan count = 0xBFFF
329 RPM Fan count = 0x3FFF
5000 RPM Fan count = 0x0438
10000 RPM Fan count = 0x021C
Internal Clock Frequency 82.8 90.0 97.2 kHz
OPEN-DRAIN DIGITAL OUTPUTS, PWM1–PWM3, XTO
Current Sink, IOL 8.0 mA
Output Low Voltage, VOL 0.4 V IOUT = −8.0 mA, VCC = 3.3 V
High Level Output Current, IOH 0.1 1 µA VOUT = VCC
OPEN-DRAIN SERIAL DATA BUS OUTPUT (SDA)
Output Low Voltage, VOL 0.4 V IOUT = −4.0 mA, VCC = 3.3 V
High Level Output Current, IOH 0.1 1 µA VOUT = VCC
SMBUS DIGITAL INPUTS (SCL, SDA)
Input High Voltage, VIH 2.0 V
Input Low Voltage, VIL 0.4 V
Hysteresis 500 mV

ADT7460
Rev. C | Page 4 of 52
Parameter1, 2, 3Min Typ4Max Unit Test Conditions/Comments
DIGITAL INPUT LOGIC LEVELS (TACH INPUTS)
Input High Voltage, VIH 2.0 V
5.5 V Maximum input voltage
Input Low Voltage, VIL +0.8 V
−0.3 V Minimum input voltage
Hysteresis 0.5 V p-p
DIGITAL INPUT LOGIC LEVELS (THERM)
Input High Voltage, VIH 1.7 V
Input Low Voltage, VIL 0.8 V
DIGITAL INPUT CURRENT
Input High Current, IIH −1 µA VIN = VCC
Input Low Current, IIL +1 µA VIN = 0
Input Capacitance, CIN 5 pF
SERIAL BUS TIMING6
Clock Frequency, fSCLK 400 kHz See Figure 2
Glitch Immunity, tSW 50 ns
Bus Free Time, tBUF 1.3 µs See Figure 2
Start Setup Time, tSU;STA 0.6 µs See Figure 2
Start Hold Time, tHD;STA 0.6 µs See Figure 2
SCL Low Time, tLOW 1.3 µs See Figure 2
SCL High Time, tHIGH 0.6 µs See Figure 2
SCL, SDA Rise Time, tR300 ns See Figure 2
SCL, SDA Fall Time, tF300 µs See Figure 2
Data Setup Time, tSU;DAT 100 ns See Figure 2
Detect Clock Low Timeout, tTIMEOUT 15 35 ms Can be optionally disabled
3Timing specifications are tested at logic levels of VIL = 0.8 V for a falling edge and at VIH = 2.0 V for a rising edge.
4Typicals are at TA= 25°C and represent the most likely parametric norm.
5The delay is the time between the round robin finishing one set of measurements and starting the next.
6Guaranteed by design, not production tested.
1All voltages are measured with respect to GND, unless otherwise specified.
2Logic inputs accept input high voltages up to VMAX even when the device is operating down to VMIN.
SCL
SD
A
PS SP
t
BUF
t
HD; STA
t
HD; DAT
t
SU; DAT
t
F
t
R
t
LOW
t
SU; STA
t
HIGH
t
HD; STA
t
SU; STO
03228-002
Figure 2. Serial Bus Timing Diagram

ADT7460
Rev. C | Page 5 of 52
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Positive Supply Voltage (VCC) 6.5 V
Voltage on Any Other Input or Output Pin −0.3 V to +6.5 V
Input Current at Any Pin ±5 mA
Package Input Current ±20 mA
Maximum Junction Temperature (TJmax) 150°C
Storage Temperature Range −65°C to +150°C
Lead Temperature, Soldering
IR Reflow Peak Temperature 220°C
IR Reflow Peak Temperature for Pb Free 260°C
Lead Temperature (Soldering 10 s) 300°C
ESD Rating 1500 V
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
16-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.

ADT7460
Rev. C | Page 6 of 52
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
03228-003
ADT7460
TOP VIEW
(Not to Scale)
1
215 PWM1/XTO
3
4
5
16
14
13
12
SCL
GND
VCC
TACH3
2/SMBALERT
SDA
+2.5VIN/SMBALERT
611
10
TACH1
7
TACH2
89
PWM3/ADDRESS ENABLE
PWM
D1+
D1–
D2+
D2–
TACH4/ADDRESS SELECT/THERM
Figure 3. Pin Configuration
Table 3. P tion Descript
Pin No. Mnemonic
in Func ions
Description
1 SCL Digital Input (Open Drain). SMBus serial clock input. Requires SMBus pull-up.
2 GND 460.Ground Pin for the ADT7
3 VCC Power Supply. Can be powered by 3.3 V standby if monitoring in low power states is required. VCC is also
monitored through this pin. The ADT7460 can also be powered from a 5 V supply. Setting Bit 7 of
Configuration Register 1 (Reg. 0x40) rescales the VCC input attenuators to correctly measure a 5 V supply.
4 TACH3 re speed of Fan 3. Can be reconfigured as anDigital Input (Open Drain). Fan tachometer input to measu
analog input (AIN3) to measure the speed of 2-wire fans.
5 PWM2 utput (Open Drain). Requires 10 kΩ typical pull-up. Pulse-width modulated output to control
SMBALERT
Digital O
Fan 2 speed.
Digital Output (Open Drain). This pin may be reconfigured as an SMBALERT interrupt output to signal
out-of-limit conditions.
6 TACH1 re speed of Fan 1. Can be reconfigured as anDigital Input (Open Drain). Fan tachometer input to measu
analog input (AIN1) to measure the speed of 2-wire fans.
7 TACH2 Digital Input (Open Drain). Fan tachometer input to measure speed of Fan 2. Can be reconfigured as an
analog input (AIN2) to measure the speed of 2-wire fans.
8 PWM3 ypicalDigital I/O (Open Drain). Pulse-width modulated output to control Fan 3/4 speed. Requires 10 kΩ t
pull-up.
ADDRESS ENABLE If pulled low on power-up, this places the ADT7460 into address select mode, and the state of Pin 9
determines the ADT7460’s slave address.
9 TACH4 put to measure speed of Fan 4. Can be reconfigured as anDigital Input (Open Drain). Fan tachometer in
analog input (AIN4) to measure the speed of 2-wire fans.
ADDRESS SELECT If in address select mode, this pin determines the SMBus device address.
THERM Alternatively, the pin may be reconfigured as a bidirectional THERM pin. Can be used to time and monit
assertions on the
or
THERM input. For example, can be connected to the PROCHOT output of Intel’s Pentium 4
processor or to the output of a trip point temperature sensor. Can be used as an output to signal
overtemperature conditions.
10 D2− Cathode Connection to Second Thermal Diode.
11 D2+ Anode Connection to Second Thermal Diode.
12 D1− Cathode Connection to First Thermal Diode.
13 D1+ Anode Connection to First Thermal Diode.
14 +2.5VIN Analog Input. Monitors 2.5 V supply, typically a chipset voltage.
SMBALERT Digital Output (Open Drain). This pin may be reconfigured as an SMBALERT interrupt output to signal
out-of-limit conditions.
15 PWM1/XTO Digital Output (Open Drain). Pulse-width modulated output to control Fan 1 speed. Requires 10 kΩ typical
pull-up.
16 SDA Digital I/O (Open Drain). SMBus bidirectional serial data. Requires SMBus pull-up.

ADT7460
Rev. C | Page 7 of 52
TYPICAL PERFORMANCE CHARACTERISTICS
LEAKAGE RESISTANCE (M Ω )
REMOTE TEMPERATURE ERROR (°C)
15
10
–20 1 3.3 100.0
10.0 30.0
0
–5
–10
–15
5DXPTOGND
DXP TO V
CC
(3.3V)
03228-004
Figure 4. Remote Temperature Error vs. Leakage Resistance
DXP–DXN CAPACITANCE (nF)
REMOTE TEMPERATURE ERROR (°C)
3
1
0
–3
–6
–9
–12
–15
–18
–21
–24
–27
2.2 3.3 4.7 10.0 22.0 47.0
–30
–33
–36
REMOTE TEMPERATURE ERROR (°C)

03228-005
Figure 5. Remote Temperature Error vs. Capacitance between D+ and D−
TEMPERATURE (°C)
REMOTE TEMPERATURE ERROR (°C)
3
–40
2
1
0
–1
–2
–3 10 60 110
–3 SIGMA
+3 SIGMA
LOW LIMIT
HIGH LIMIT
03228-006
TEMPERATURE (°C)
LOCAL TEMPERATURE ERROR (°C)
–3
–40 10 110
60
1
0
–2
–1
3
2
LOW LIMIT
HIGH LIMIT
–3 SIGMA
+3 SIGMA
03228-007
Figure 7. Local Temperature Error vs. Actual Temperature
FREQUENCY (Hz)
REMOTE TEMPERATURE ERROR (°C)
14
12
–2
100k 550k 50M
5M
6
4
0
2
10
8
100mV
250mV
03228-008
Figure 8. Remote Temperature Error vs. Power Supply Noise Frequency
RROR (°C)
12.5
10.0
–5.0
100k 550k 50M
FREQUENCY (Hz)
LOCAL TEMPERATURE
5M
5.0
2.5
–2.5
0
7.5
100mV
E
250mV
03228-009
Figure 9. Local Temperature Error vs. Power Supply Noise Frequency
Figure 6. Remote Temperature Error vs. Actual Temperature

ADT7460
Rev. C | Page 8 of 52
1.90
1.85
1.80
1.75
1.70
1.65
1.60
1.55
1.50
1.45
1.40
2.5
2.6 3.0 3.4 3.8 4.2 4.6 5.0 5.4
5.5
SUPPLYVOLTAGE (V)
SUPPLY CURRENT (mA)
03228-010
Figure 10. Supply Current vs. Supply Voltage
FREQUENCY (Hz)
REMOTE TEMPERATURE ERROR (°C)
16
60k
14
12
10
8
6
4
2
0
–2 110k 1M 10M 50M
10mV
20mV
03228-011
Figure 11. Remote Temperature Error vs. Differential Mode Noise Frequency
10k FREQUENCY (Hz)
REMOTE TEMPERATURE ERROR (°C)
40
35
30
25
20
15
10
5
0
–5
–10 100k 1M 10M
20mV
40mV
100mV
03228-012
Figure 12. Remote Temperature Error vs. Common-Mode Noise Frequency

ADT7460
Rev. C | Page 9 of 52
PRODUCT DESCRIPTION
The ADT7460 is a thermal monitor and multiple fan controller
for any system requiring monitoring and cooling. The device
communicates with the system via a serial System Management
Bus (SMBus). The serial bus controller has an optional address
line for device selection (Pin 9), a serial data line for reading
and writing addresses and data (Pin 16), and an input line for
the serial clock (Pin 1). All control and programming functions
of the ADT7460 are performed over the serial bus. In addition,
two of the pins can be reconfigured as an SMBALERT output to
indicate out-of-limit conditions.
MEASUREMENT INPUTS
The device has three measurement inputs, one for voltage and
two for temperature. It can also measure its own supply voltage
and can measure ambient temperature with its on-chip
temperature sensor.
Pin 14 is an analog input with an on-chip attenuator and is
configured to monitor 2.5 V.
Power is supplied to the chip via Pin 3, and the system also
monitors VCC through this pin. In PCs, this pin is normally
connected to a 3.3 V standby supply. This pin can, however, be
connected to a 5 V supply and monitor it without overranging.
Remote temperature sensing is provided by the D1± and D2±
inputs, to which diode-connected, external temperature-sensing
transistors, such as a 2N3904 or CPU thermal diode, may be
connected.
The ADC also accepts input from an on-chip band gap
temperature sensor, which monitors system ambient
temperature.
SEQUENTIAL MEASUREMENT
When the ADT7460 monitoring sequence is started, it cycles
sequentially through the measurement of 2.5 V input and the
temperature sensors. Measured values from these inputs are
stored in value registers. These can be read out over the serial
bus or can be compared with programmed limits stored in the
limit registers. The results of out-of-limit comparisons are
stored in the status registers, which can be read over the serial
bus to flag out-of-limit conditions.
RECOMMENDED IMPLEMENTATION
Configuring the ADT7460 as in Figure 13 allows the systems
designer the following features:
•Two PWM outputs for fan control of up to three fans (the
front and rear chassis fans are connected in parallel).
•Three TACH fan speed measurement inputs.
•VCC measured internally through Pin 3.
•CPU temperature measured using Remote 1 temperature
channel.
•Ambient temperature measured through Remote 2
temperature channel.
•Bidirectional THERM pin. Allows Intel Pentium 4
PROCHOT monitoring and can function as an
overtemperature THERM output.
•SMBALERT system interrupt output.
ICH
TACH2
D1+
D1–
D2+
D2–
TACH1
P
AMBIENT
TEMPERATURE
PWM3
TACH3
GND
ADT7460
SCL
SMBALERT
SDA
WM1
THERM PROCHOT
FRONT
CHASSIS
3228-013
FAN
REAR
CHASSIS
FAN
Figure 13. Recommended Implementation

ADT7460
Rev. C | Page 10 of 52
DRES
-functio
ADT7460 AD S SELECTION
n PWMPin 8 is the dual 3/ADDRESS ENABLE pin. If
ower-up, the ADT7460 reads the state of
Pin 8 is pulled low on p
ACH4/ADDRE
Pin 9 (T SS SELECT/THERM) to determine the
s. If Pin 8 i
ADT7460’s slave addres s high on power-up, the
7460 defaults to SM
ribed in more de
Table 41 to Table 81 describe the registers in more detail.
Table 4. Summary Inte
ADT Bus Slave Address 0x2E. This function
is desc tail later.
INTERNAL REGISTERS OF THE ADT7460
Table 4 summarizes the ADT7460’s principal internal registers.
rnal Registers
Register Description
Configuration These registers provide control and configuration of the ADT7460, including alternate pinout functionality.
Address Pointer This register contains the address that selects one of the other internal registers. When writing to the ADT7460, the
first byte of data is always a register address, which is written to the address pointer register.
Status Registers These registers provide the status of each limit comparison and are used to signal out-of-limit conditions on the
temperature, voltage, or fan speed channels. If Pin 14 or Pin 5 is configured as SMBALERT, this pin asserts low
whenever an unmasked status bit is set.
Interrupt Mask These registers allow each interrupt status event to be masked when Pin 14 or Pin 5 is configured as an SMBALERT
output.
Value and Limit The results of analog voltage input, temperature, and fan speed measurements are stored in these registers, along
with their limit values.
Offset These registers allow each temperature channel reading to be offset by a twos complement value written to these
registers.
TMIN These registers program the starting temperature for each fan under automatic fan speed control.
TRANGE These registers program the temperature-to-fan speed control slope in automatic fan speed control mode for each
PWM output.
Operating Point These registers define the target operating temperatures for each thermal zone when running under dynamic TMIN
control. This function allows the cooling solution to adjust dynamically in response to measured temperature and
system performance.
Enhance Acoustics These registers allow each PWM output controlling fan to be tweaked to enhance the system’s acoustics.