dBCool® Remote Thermal
Monitor and Fan Controller
ADT7475
FEATURES
GENERAL DESCRIPTION
Controls and monitors up to 4 fans
The ADT7475 dBCool 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 they operate at the
lowest possible speed for minimum acoustic noise.
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
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
input.
THERM
The ADT7475 also provides critical thermal protection to the
system using the bidirectional pin as an output to
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)
THERM
prevent system or component overheating.
Fully RoHS compliant
FUNCTIONAL BLOCK DIAGRAM
SCL SDA SMBALERT
ADT7475
SERIAL BUS
INTERFACE
PWM
PWM1
REGISTERS
AND
ACOUSTIC
ENHANCEMENT
CONTROL
AUTOMATIC
FAN SPEED
CONTROL
PWM2
PWM3
CONTROLLERS
(HF AND LF)
ADDRESS
POINTER
REGISTER
PWM
TACH1
TACH2
TACH3
TACH4
CONFIGURATION
REGISTERS
FAN
SPEED
COUNTER
INTERRUPT
MASKING
PERFORMANCE
MONITORING
INTERRUPT
STATUS
REGISTERS
THERMAL
PROTECTION
THERM
V
TOADT7475
CC
V
CC
D1+
D1–
D2+
D2–
INPUT
SIGNAL
LIMIT
10-BIT
ADC
COMPARATORS
CONDITIONING
AND
ANALOG
MULTIPLEXER
VALUE AND
LIMIT
REGISTERS
V
CCP
BAND GAP
REFERENCE
BAND GAP
TEMPERATURE
SENSOR
GND
Figure 1.
Rev. A
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