Product Description; Comparison Between Adt7467 And Adt7473/Adt7473-1; How To Set The Functionality Of Pin 9; Recommended Implementation - Analog Devices ADT7473 Manual

PRODUCT DESCRIPTION

The ADT7473/ADT7473-1 is a complete thermal monitor and
multiple fan controller for any system requiring thermal mon-
itoring 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 con-
trol and programming functions for the ADT7473/ADT7473-1
are performed over the serial bus. Additionally, a pin can be
reconfigured as an SMBALERT output to signal out-of-limit
conditions.
Table 5 illustrates the differences between the ADT7473 and the
ADT7473-1.
Table 5. ADT7473/ADT7473-1 Device Comparison
Feature ADT7473
Pin 5 Default:
PWM2
SMBus Address Fixed address
Remote Ch. 2 = 100°C
Therm. Limit
Register 0x30, Default: 0x00
0x31, 0x32
Register 0x3F Default: 0x68
Revision Register
Register 0x40, Bit 7 Reserved
Register 0x42, Bit 0 Reserved
Registers 0x5C, Default: 0x82
0x5D, 0x5E
Register 0x7C, Bit 4 Reserved
Register 0x7D, Bit 4 Reserved
COMPARISON BETWEEN ADT7467 AND
ADT7473/ADT7473-1
The following list shows some comparisons between the
ADT7467 and the ADT7473/ADT7473-1:
•
The ADT7473/ADT7473-1 can be powered via a 3.3 V
supply only, and does not support 5 V operation, while the
ADT7467 does. Violating this specification results in
irreversible damage to the ADT7473/ADT7473-1. See the
ADT7473/ADT7473-1 Specifications section for more
information.
ADT7473-1
Default: THERM_LATCH
Address selectable
= 136°C
Default: 0xFF
Default: 0x69
(R/W)
1 = Reset Latch
(lockable)
(Read-only)
1 = THERM Limit
Latched
Default: 0x62
THERM Output
Hysteresis
THERM_LATCH
Configuration
0 = Remote Channel 2
1 = Remote Channel 1
and Remote Channel 2
Rev. C | Page 9 of 72
•
A high frequency PWM drive can be independently selected
for each PWM channel on the ADT7473/ADT7473-1. 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/ADT7473-1 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/ADT7473-1.

HOW TO SET THE FUNCTIONALITY OF PIN 9

Pin 9 on the ADT7473/ADT7473-1 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 (0x7D).
Table 6. Pin 9 Settings
Bit 0 Bit 1 Function
0 0 TACH4
0 1 THERM
1 0
SMBALERT
1 1 GPIO

RECOMMENDED IMPLEMENTATION

Configuring the ADT7473 as shown in Figure 14 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/ADT7473-1