Product Description; Comparison Between Adt7467 And Adt7473; How To Set The Functionality Of Pin 9; Recommended Implementation - Analog Devices dBCool ADT7473 Manual

ADT7473
PRODUCT DESCRIPT
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 bu
data line for reading and writing addresses and data (Pin 16),
and an input line for the serial clock (Pin 1). All control an
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 ADT747
The following list shows some comparisons between the
ADT7467 and the ADT7473:
•
The ADT7473 can be powered via a 3.3 V supply only, and
does not support 5 V operation, while the AD
Violating this specification results in irreversible damage
to the ADT7473. See the ADT7473 Specifications sectio
for more information.
•
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 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 not supported on the
ADT7473.
ION
s controller has a serial
d
T7467 does.
FRONT
CHASSIS
FAN
REAR
CHASSIS
FAN
AMBIENT
TEMPERATURE
Fig ure 13. ADT7473 Co
Rev. A | Page 10 of 76

HOW TO SET THE FUNCTIONALITY OF PIN 9

Pin 9 on the ADT7473 has four possible functions: SMBA
THERM , GPIO, and TACH4. The user chooses the required
functionality by setting Bit 0 and Bit 1 of Configuration
Register 4 (0x7D).
Table 5. Pin 9 Settings
Bit 0 Bit 1
0 0
0 1
3
1 0
1 1

RECOMMENDED IMPLEMENTATION

Configuring the ADT7473, as shown in Figure 13, allows the
system designer to use the following features:
n •
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
SMB ALERT
GND
nfiguration
Function
TACH4
THERM
SMBALERT
GPIO
CPU FAN
CPU
ICH
,
LERT