ADT7476ARQZ-R7 datasheet(33/67 Pages) ONSEMI

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ADT7476

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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 ADT7476 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 ADT7476 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

ADT7476, 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 ADT7476 be physically located in

the system?

This influences the assignment of the temperature

measurement channels to particular system thermal zones.

For example, locating the ADT7476 close to the VRM

controller circuitry allows the VRM temperature to be

monitored using the local temperature channel.

Figure 48. Hardware Configuration Example

REAR CHASSIS

FRONT CHASSIS

CPU FAN SINK

REMOTE 1 =

AMBIENT TEMP

LOCAL =

VRM TEMP

REMOTE 2 =

CPU TEMP

PWM1

PWM2

TACH1

TACH2

TACH3

PWM3

MUX

THERMAL CALIBRATION

TMIN

TRANGE

THERMAL CALIBRATION

100%

TMIN

TRANGE

THERMAL CALIBRATION

100%

TMIN

TRANGE

PWM

MIN

PWM

MIN

PWM

MIN

100%

PWM

GENERATOR

PWM

GENERATOR

TACHOMETER 3

AND 4

MEASUREMENT

TACHOMETER 1

MEASUREMENT

TACHOMETER 2

MEASUREMENT

RAMP

CONTROL

(ACOUSTIC

ENHANCEMENT)

RAMP

CONTROL

(ACOUSTIC

ENHANCEMENT)

RAMP

CONTROL

(ACOUSTIC

ENHANCEMENT)

PWM

GENERATOR

PWM

CONFIG

PWM

CONFIG

PWM

CONFIG

ADT7476ARQZ-R7 Datasheet(PDF) 33 Page - ON Semiconductor

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