dBCool
®
Remote Thermal
Controller and Voltage Monitor
ADT7468
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 T
MIN
control mode intelligently optimizes system
acoustics
Automatic fan speed control mode manages 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
dBCool
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 T
MIN
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
SCL
VID5
VID4
VID3
VID2
VID1
VID0
PWM1
PWM2
PWM3
PWM REGISTERS
AND
CONTROLLERS
HF & LF
ACOUSTIC
ENHANCEMENT
CONTROL
AUTOMATIC
FAN SPEED
CONTROL
ADDRESS
POINTER
REGISTER
ACOUSTIC
ENHANCEMENT
CONTROL
SERIAL BUS
INTERFACE
SDA SMBALERT
TACH1
TACH2
TACH3
TACH4
PERFORMANCE
MONITORING
THERM
V
CC
TO ADT7468
THERMAL
PROTECTION
FAN SPEED
COUNTER
DYNAMIC
T
MIN
CONTROL
PWM
CONFIGURATION
REGISTERS
INTERRUPT
MASKING
INTERRUPT
STATUS
REGISTERS
V
CC
D1+
D1–
D2+
D2–
+5V
IN
+12V
IN
+2.5V
IN
V
CCP
ADT7468
10-BIT
ADC
INPUT
SIGNAL
CONDITIONING
AND
ANALOG
MULTIPLEXER
LIMIT
COMPARATORS
SRC
BAND GAP
REFERENCE
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. Trademarks and
registered trademarks are the property of their respective owners.
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
© 2005 Analog Devices, Inc. All rights reserved.
04499-0-001
BAND GAP
TEMP SENSOR
ADT7468
TABLE OF CONTENTS
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
ESD Caution.................................................................................. 5
Pin Configuration and Function Descriptions............................. 6
Typical Performance Characteristics ............................................. 8
Product Description....................................................................... 10
Comparison between ADT7463 and ADT7468..................... 10
Recommended Implementation............................................... 11
Serial Bus Interface......................................................................... 12
Write Operations ........................................................................ 13
Read Operations ......................................................................... 14
SMBus Timeout .......................................................................... 14
VID Code Monitoring ................................................................... 15
VID Code Registers.................................................................... 15
Analog-to-Digital Converter ........................................................ 16
Voltage Measurement Input...................................................... 16
Additional ADC Functions for Voltage Measurements ........ 16
Temperature Measurement ....................................................... 18
Additional ADC Functions for
Temperature Measurement ....................................................... 21
Limits, Status Registers, and Interrupts....................................... 22
Limit Values................................................................................. 22
Status Registers ........................................................................... 23
Interrupts..................................................................................... 23
Active Cooling ................................................................................ 28
Driving the Fan Using PWM Control ..................................... 28
Laying Out 2-Wire and 3-Wire Fans ....................................... 30
Fan Speed Measurement............................................................ 31
Fan Spin-Up ................................................................................ 33
Step 12: Ramp Rate for Acoustic Enhancement..................... 57
Enhancing System Acoustics ........................................................ 60
Acoustic Enhancement Mode Overview ................................ 60
Register Tables ................................................................................ 62
ADT7468 Programming Block Diagram .................................... 81
Outline Dimensions ....................................................................... 82
Ordering Guide .......................................................................... 82
PWM Logic State........................................................................ 34
Fan Speed Control...................................................................... 34
Miscellaneous Functions ............................................................... 35
Operating from 3.3 V Standby ................................................. 35
XNOR Tree Test Mode .............................................................. 35
Power-On Default ...................................................................... 35
Automatic Fan Control Overview................................................ 37
Dynamic T
MIN
Control Mode ................................................... 38
Programming the Automatic Fan Speed Control Loop ............ 40
Step 1: Hardware Configuration .............................................. 40
Step 2: Configuring the Mux .................................................... 43
Step 3: T
MIN
Settings for Thermal Calibration Channels ...... 45
Step 4: PWM
MIN
for Each PWM (Fan) Output ...................... 46
Step 5: PWM
MAX
for PWM (Fan) Outputs.............................. 46
Step 6: T
RANGE
for Temperature Channels................................ 47
Step 7: T
THERM
for Temperature Channels ............................... 50
Step 8: T
HYST
for Temperature Channels.................................. 51
Step 9: Operating Points for Temperature Channels............. 52
Step 10: High and Low Limits for Temperature Channels ... 53
Step 11: Monitoring THERM ................................................... 56
REVISION HISTORY
7/05—Rev. 0 to Rev. A
Changes to Absolute Maximum Ratings ................................... 5
Changes to Table 17.................................................................... 62
Changes to Ordering Guide ...................................................... 80
4/04—Revision 0: Initial Version
Rev. A | Page 2 of 84
ADT7468
SPECIFICATIONS
T
A
= T
MIN
to T
MAX
, V
CC
= V
MIN
to V
MAX
, unless otherwise noted.
All voltages are measured with respect to GND, unless otherwise specified. Typicals are at T
A
= 25°C and represent most likely parametric
norms. Logic inputs accept input high voltages up to V
MAX
even when device is operating down to V
MIN
. Timing specifications are tested at
logic levels of V
IL
= 0.8 V for a falling edge and V
IH
= 2.0 V for a rising edge. SMBus timing specifications are guaranteed by design and
are not production tested.
Table 1.
Parameter
POWER SUPPLY
Supply Voltage
Supply Current, I
CC
TEMP-TO-DIGITAL CONVERTER
Local Sensor Accuracy
−3.5
−4
Resolution
Remote Diode Sensor Accuracy
−3.5
−4.5
Resolution
Remote Sensor Source Current
0.25
6
36
96
0.25
±1.5
+2
+2
Min
3.0
Typ
3.3
Max
5.5
3
20
±1.5
+2
+2
Unit
V
mA
μA
°C
°C
°C
°C
°C
°C
°C
°C
μA
μΑ
μΑ
Test Conditions/Comments
Interface inactive, ADC active
Standby mode
0°C ≤ T
A
≤ 70°C
−40°C ≤ T
A
≤ +100°C
−40°C ≤ T
A
≤ +120°C
0°C ≤ T
A
≤ 70°C; 0°C ≤ T
D
≤ 120°C
−40°C ≤ T
A
≤ +100°C; 0°C ≤ T
D
≤ +120°C
−40°C ≤ T
A
≤ +120°C; 0°C ≤ T
D
≤ +120°C
First current
Second current
Third current
ANALOG-TO-DIGITAL CONVERTER
(INCLUDING MUX AND ATTENUATORS)
Total Unadjusted Error (TUE)
Differential Nonlinearity (DNL)
Power Supply Sensitivity
Conversion Time (Voltage Input)
Conversion Time (Local Temperature)
Conversion Time (Remote Temperature)
Total Monitoring Cycle Time
Total Monitoring Cycle Time
Input Resistance
FAN RPM-TO-DIGITAL CONVERTER
Accuracy
±2
±1.5
±1
±0.1
11
12
38
145
19
70
140
40
80
100
200
±5
±7
±10
65,535
%
%
LSB
%/V
ms
ms
ms
ms
ms
kΩ
kΩ
%
%
%
RPM
RPM
RPM
RPM
For 12 V and 5 V channels
For all other channels
8 bits
Averaging enabled
Averaging enabled
Averaging enabled
Averaging enabled
Averaging disabled
For V
CC
channel
For all other channels
0°C ≤ T
A
≤ 70°C , 3.3 V
−40°C ≤ T
A
≤ +120°C , 3.3 V
−40°C ≤ T
A
≤ +120°C , 5.5 V
Fan count = 0xBFFF
Fan count = 0x3FFF
Fan count = 0x0438
Fan count = 0x021C
0°C ≤ T
A
≤ 70°C, V
CC
= 3.3 V
−40°C ≤ T
A
≤ +120°C, V
CC
= 3.3 V
−40°C ≤ T
A
≤ +120°C, V
CC
= 5.5 V
Full-Scale Count
Nominal Input RPM
109
329
5000
10000
85.5
83.7
81
90
90
90
94.5
96.3
99
Internal Clock Frequency
kHz
kHz
kHz
Rev. A | Page 3 of 84
ADT7468
Parameter
OPEN-DRAIN DIGITAL OUTPUTS,
PWM1 TO PWM3, XTO
Current Sink, I
OL
Output Low Voltage, V
OL
High Level Output Current, I
OH
OPEN-DRAIN SERIAL DATA BUS OUTPUT (SDA)
Output Low Voltage, V
OL
High Level Output Current, I
OH
SMBUS DIGITAL INPUTS (SCL, SDA)
Input High Voltage, V
IH
Input Low Voltage, V
IL
Hysteresis
DIGITAL INPUT LOGIC LEVELS (TACH INPUTS)
Input High Voltage, V
IH
Input Low Voltage, V
IL
−0.3
Hysteresis
DIGITAL INPUT LOGIC LEVELS (THERM) ADTL+
Input High Voltage, V
IH
Input Low Voltage, V
IL
DIGITAL INPUT CURRENT
Input High Current, I
IH
Input Low Current, I
IL
Input Capacitance, C
IN
SERIAL BUS TIMING
Clock Frequency, f
SCLK
Glitch Immunity, t
SW
Bus Free Time, t
BUF
Start Setup Time, t
SU;STA
Start Hold Time, t
HD;STA
SCL Low Time, t
LOW
SCL High Time, t
HIGH
SCL, SDA Rise Time, t
R
SCL, SDA Fall Time, t
F
Data Setup Time, t
SU;DAT
Data Hold Time, t
HD;DAT
Detect Clock Low Timeout, t
TIMEOUT
0.5
0.75 × V
CCP
0.4
−1
1
5
10
4.7
4.7
4.0
4.7
4.0
400
50
Min
Typ
Max
Unit
Test Conditions/Comments
0.1
8.0
0.4
1.0
0.4
1.0
mA
V
μA
V
μA
V
V
mV
V
V
V
V
V p-p
V
V
μA
μA
pF
kHz
ns
μs
μs
μs
μs
μs
ns
μs
ns
ns
ms
I
OUT
= −8.0 mA, V
CC
= +3.3 V
V
OUT
= V
CC
I
OUT
= −4.0 mA, V
CC
= +3.3 V
V
OUT
= V
CC
0.1
2.0
0.4
500
2.0
5.5
0.8
Maximum input voltage
Minimum input voltage
V
IN
= V
CC
V
IN
= 0
See Figure 2
50
1000
300
250
300
15
35
Can be optionally disabled
t
LOW
SCL
t
R
t
F
t
HD; STA
t
HIGH
t
HD; STA
t
HD; DAT
t
SU; DAT
t
SU; STA
t
SU; STO
SDA
t
BUF
P
S
S
P
Figure 2. Serial Bus Timing Diagram
Rev. A | Page 4 of 84
04499-0-002
ADT7468
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Positive Supply Voltage (V
CC
)
Maximum Voltage on 12 V
IN
Pin
Voltage on Any Input or Output Pin
Input Current at Any Pin
Package Input Current
Maximum Junction Temperature (T
JMAX
)
Storage Temperature Range
Lead Temperature, Soldering
IR Reflow Peak Temperature
For Pb-free
Lead Temperature (Soldering 10 sec)
ESD Rating
Rating
5.5 V
20 V
−0.3 V to +6.5 V
±5 mA
±20 mA
150°C
−65°C to +150°C
220°C
260°C
300°C
1000 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
24-lead QSOP package:
θ
JA
= 150°C/W
θ
JC
= 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.
Rev. A | Page 5 of 84
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