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STEP 1: HARDWARE CONFIGURATION
During system design, the motherboard sensing and control
capabilities should be addressed early in the design stages.
Decisions about how these capabilities are used should involve
the system thermal/mechanical engineer. Consider the
following questions:
1.
What ADT7473 functionality will be used?
•
PWM2 or SMBALERT ?
•
TACH4 fan speed measurement or overtemperature
THERM function?
The ADT7473 offers multifunctional pins that can be
reconfigured to suit different system requirements and
physical layouts. These multifunction pins are software
programmable.
REMOTE 1 =
AMBIENT TEMP
LOCAL =
VRM TEMP
REMOTE 2 =
CPU TEMP
THERMAL CALIBRATION
100%
0%
T
T
MIN
RANGE
THERMAL CALIBRATION
100%
0%
T
T
MIN
RANGE
THERMAL CALIBRATION
100%
0%
T
T
MIN
RANGE
Figure 45. Hardware Configuration Example
2.
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.
3.
Is the CPU fan to be controlled using the ADT7473 or will
it run at full speed 100% of the time?
If run at 100%, this frees up a PWM output, but the system
is louder.
4.
Where will the ADT7473 be physically located in the
system?
This influences the assignment of the temperature
measurement channels to particular system thermal zones.
For example, locating the ADT7473 close to the VRM
controller circuitry allows the VRM temperature to be
monitored using the local temperature channel.
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 1
MEASUREMENT
PWM
MIN
RAMP
CONTROL
MUX
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 2
MEASUREMENT
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 3
AND 4
MEASUREMENT
Rev. 0 | Page 33 of 76
PWM
CONFIG
PWM
PWM1
GENERATOR
TACH1
PWM
CPU FAN SINK
CONFIG
PWM
PWM2
GENERATOR
TACH2
PWM
CONFIG
FRONT CHASSIS
PWM
PWM3
GENERATOR
TACH3
REAR CHASSIS
ADT7473
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