dBCool™ Remote Thermal
Monitor and Fan Controller
ADT7475
Preliminary Technical Data
FEATURES
GENERAL DESCRIPTION
Controls and monitors up to 4 fans
High and low frequency fan drive signal
The ADT7475 dBCOOLTM controller is a thermal monitor and
multiple PWM fan controller for noise-sensitive or power-
sensitive applications requiring active system cooling. The
ADT7475 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.
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
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
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
THERM
be monitored using the
provides critical thermal protection to the system using the
THERM
input. The ADT7475 also
bidirectional
pin as an output to prevent system or
component overheating.
Meets SMBus 2.0 electrical specifications
(fully SMBus 1.1 compliant)
Fully ROHS compliant
FUNCTIONAL BLOCK DIAGRAM
SCL SDA SMBALERT
SERIAL BUS
INTERFACE
ADDRESS
POINTER
REGISTER
AUTOMATIC
FAN SPEED
CONTROL
ACOUSTIC
ENHANCEMENT
CONTROL
PWM1
PWM2
PWM3
PWM REGISTERS
AND
CONTROLLERS
HF & LF
PWM
CONFIGURATION
REGISTERS
DYNAMIC
T
MIN
TACH1
TACH2
TACH3
TACH4
CONTROL
FAN SPEED
COUNTER
INTERRUPT
MASKING
PERFORMANCE
MONITORING
THERMAL
PROTECTION
THERM
INTERRUPT
STATUS
REGISTERS
V
TOADT7475
SRC
CC
V
ADT7475
CC
D1+
D1–
D2+
D2–
LIMIT
COMPARATORS
INPUT
SIGNAL
CONDITIONING
AND
10-BIT
ADC
ANALOG
MULTIPLEXER
VALUE AND
LIMIT
V
CCP
BAND GAP
REFERENCE
REGISTERS
BAND GAP
TEMP SENSOR
GND
Figure 1.
Rev. PrC
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
Fax: 781.326.8703
www.analog.com
© 2005 Analog Devices, Inc. All rights reserved.
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