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PRODUCT DESCRIPTION
The ADT7473 is a complete thermal monitor and multiple fan
controller for any system requiring thermal monitoring and
cooling. The device communicates with the system via a serial
system management bus. The serial bus controller has 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 for the ADT7473 are performed over
the serial bus. Additionally, a pin can be reconfigured as an
SMBALERT output to signal out-of-limit conditions.
COMPARISON BETWEEN ADT7467 AND ADT7473
The ADT7473 can only be powered via a 3.3 V supply, and does
not support 5 V operation like the ADT7467.
High frequency PWM drive can be independently selected for
each PWM channel on the ADT7473. This is not available on
the ADT7467.
The range and resolution of the temperature offset register can
now be changed from a ±64°C range at 0.5°C resolution to a
±128°C range at 1°C resolution. This is not available on the
ADT7467.
THERM overtemperature events can be disabled/enabled
individually on each temperature channel. This is not available
on the ADT7467.
Bit 7 of Configuration Register 1 is no longer supported because
the ADT7473 cannot be powered via a 5 V supply.
Bit 0 of Configuration Register 1 (0x40) remains writable after
the lock bit is set. This bit enables monitoring.
2-wire fan speed measurement is no longer supported on the
ADT7473.
FRONT
CHASSIS
FAN
REAR
CHASSIS
FAN
AMBIENT
TEMPERATURE
Figure 13. ADT7473 Configuration
How to Set the Functionality of Pin 9
Pin 9 on the ADT7473 has four possible functions: SMBALERT ,
THERM , GPIO, and TACH4. The user chooses the required
functionality by setting Bit 0 and Bit 1 of Configuration
Register 4 at Address 0x7D.
Table 4. Pin 9 Settings
Bit 0
Bit 1
0
0
0
1
1
0
1
1
RECOMMENDED IMPLEMENTATION
Configuring the ADT7473, as shown in Figure 13, allows the
system designer to use 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.
•
V
measured internally through Pin 3.
CC
•
CPU temperature measured using Remote 1 temperature
channel.
•
Ambient temperature measured through Remote 2
temperature channel.
•
Bidirectional THERM pin. This feature allows Intel
Pentium 4 PROCHOT monitoring and can function as an
overtemperature THERM output. It can alternatively be
programmed as an SMBALERT system interrupt output.
ADT7473
PWM1
TACH2
TACH1
PWM3
D2+
TACH3
D2–
THERM
PROCHOT
D1+
SDA
D1–
SCL
SMBALERT
GND
Rev. 0 | Page 9 of 76
Function
TACH4
THERM
SMBALERT
GPIO
CPU FAN
CPU
ICH
ADT7473
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