ADT7467 Analog Devices, Inc., ADT7467 Datasheet - Page 38

• Manufacturer Part Number: ADT7467
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

ADT7467
PROGRAMMING THE AUTOMATIC FANSPEED CONTROL LOOP
To more efficiently understand the automatic fan speed control
loop, it is strongly recommended to use the ADT7467
evaluation board and software while reading this section.
This section provides the system designer with an understand-
ing of the automatic fan control loop and provides step-by-step
guidance on effectively evaluating and selecting critical system
parameters. To optimize the system characteristics, the designer
should consider several aspects of the system configuration,
including the number of fans, where fans are located, and what
temperatures are measured.
The mechanical or thermal engineer who is tasked with the
system thermal characterization should also be involved at the
beginning of the process.
STEP 1: HARDWARE CONFIGURATION
The motherboard sensing and control capabilities should be
addressed in the early stages of designing a system, and
decisions about how these capabilities are used should involve
the system’s thermal/mechanical engineer. Ask the following
questions:
1.
What ADT7467 functionality will be used?
•
•
PWM2 or SMBALERT
TACH4 fan speed measurement or overtemperature
THERM function
AMBIENT TEMP
REMOTE 1 =
REMOTE 2 =
VRM TEMP
CPU TEMP
LOCAL =
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
T
T
T
MIN
MIN
MIN
T
T
T
RANGE
RANGE
RANGE
100%
100%
100%
0%
0%
0%
Figure 53. Hardware Configuration Example
MUX
Rev. A | Page 38 of 80
PWM
PWM
PWM
MIN
MIN
MIN
2.
3.
4.
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
•
•
The ADT7467 offers multifunctional pins that can be
reconfigured to suit different system requirements and
physical layouts. These multifunction pins are software
programmable.
How many fans will be supported in the system, three or
four? This influences the choice of whether to use the
TACH4 pin or to reconfigure it for the THERM function.
Will the CPU fan be controlled using the ADT7467, or will
it run at full speed 100% of the time?
Running it at 100% frees up a PWM output, but the system
is louder.
Where will the ADT7467 be physically located in the
system?
This influences the assignment of the temperature
measurement channels to particular system thermal zones.
For example, locating the ADT7467 close to the VRM
controller circuitry allows the VRM temperature to be
monitored using the local temperature channel.
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
RAMP
RAMP
RAMP
AND 4
5 V voltage monitoring or overtemperature THERM
function
12 V voltage monitoring or VID5 input
GENERATOR
GENERATOR
GENERATOR
CONFIG
CONFIG
CONFIG
PWM
PWM
PWM
PWM
PWM
PWM
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
FRONT CHASSIS
REAR CHASSIS
CPU FAN SINK