dB
Cool Remote Thermal
Controller and Voltage Monitor
ADT7476
Rev. B
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.
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Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2005–2007 Analog Devices, Inc. All rights reserved.
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
dB
Cool® 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
0
538
2-
0
01
ACOUSTIC
ENHANCEMENT
CONTROL
BAND GAP
REFERENCE
10-BIT
ADC
INTERRUPT
MASKING
PWM
CONFIGURATION
REGISTERS
ADDRESS
POINTER
REGISTER
VALUE AND
LIMIT
REGISTERS
LIMIT
COMPARATORS
INTERRUPT
STATUS
REGISTERS
INPUT
SIGNAL
CONDITIONING
AND
ANALOG
MULTIPLEXER
V
CC
TO ADT7476
V
CC
D1+
D1–
D2+
D2–
+5V
IN
+12V
IN
+2.5V
IN
V
CCP
VID/GPIO
REGISTER
VID5
VID4/GPIO4
VID3/GPIO3
VID2/GPIO2
VID1/GPIO1
VID0/GPIO0
GPIO6
SERIAL BUS
INTERFACE
SCL SDA SMBALERT
SMBus
ADDRESS
SELECTION
ADDR
SELECT
ADDREN
GND
PWM1
PWM2
PWM3
PWM
REGISTERS
AND
CONTROLLERS
(HF AND LF)
AUTOMATIC
FAN SPEED
CONTROL
TACH1
TACH2
TACH3
TACH4
FAN
SPEED
COUNTER
THERMAL
PROTECTION
PERFORMANCE
MONITORING
THERM
BAND GAP
TEMP. SENSOR
ADT7476
Figure 1.
www.BDTIC.com/ADI
