ADT7476AARQZ-R datasheet(35/69 Pages) ONSEMI

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ADT7476A

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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.

Ask the following questions:

1. What ADT7476A functionality is used?

• PWM2 or SMBALERT?

• TACH4 fan speed measurement or

overtemperature THERM function?

• 2.5 V voltage monitoring or overtemperature

THERM function?

• 12 V voltage monitoring or VID5 input?

The ADT7476A offers multifunctional pins that

can be reconfigured to suit different system

requirements and physical layouts. These

multifunction pins are software programmable.

2. How many fans are supported in 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

ADT7476A, or will the CPU fan 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 ADT7476A be physically located

in the system?

This influences the assignment of the temperature

measurement channels to particular system

thermal zones. For example, locating the

ADT7476A close to the VRM controller circuitry

allows the VRM temperature to be monitored

using the local temperature channel.

Figure 48. Hardware Configuration Example

THERMAL CALIBRATION

REMOTE1 =

AMBIENT TEMP

100%

TMIN

TRANGE

PWM

MIN

MUX

TACHOMETER1

MEASUREMENT

PWM

MIN

PWM

MIN

THERMAL CALIBRATION

100%

TMIN

TRANGE

THERMAL CALIBRATION

100%

TMIN

TRANGE

LOCAL =

VRM TEMP

REMOTE2 =

CPU TEMP

TACHOMETER2

MEASUREMENT

RAMP

CONTROL

(ACOUSTIC

ENHANCEMENT)

TACHOMETER3

AND 4

MEASUREMENT

PWM

CONFIG

PWM

GENERATOR

PWM1

PWM2

PWM3

TACH3

TACH2

TACH1

CPU FAN SINK

FRONT CHASSIS

REAR CHASSIS

RAMP

CONTROL

(ACOUSTIC

ENHANCEMENT)

RAMP

CONTROL

(ACOUSTIC

ENHANCEMENT)

PWM

CONFIG

PWM

GENERATOR

PWM

CONFIG

PWM

GENERATOR

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