ADT7467ARQZ-R7 datasheet(10/77 Pages) ONSEMI

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ADT7467

Rev. 3 | Page 10 of 77 | www.onsemi.com

Configuration Register 5

Bit 0: If Bit 0 is set to 1, the ADT7467, in terms of temperature,

is backward compatible with the ADT7460. Measurements,

including TMIN calibration circuit and fan control, work in the

range −127°C to +127°C. In addition, care should be taken in

reprogramming the temperature limits (TMIN, operating point,

THERM) to their desired twos complement value, because the

power-on default for them is at Offset 64. The extended

temperature range is −64°C to 191°C. The default is 1, which is

in the −64°C to +191°C temperature range.

Bit 1 = 0 is the high frequency (22.5 kHz) fan drive signal.

Bit 1 = 1 switches the fan drive to low frequency PWM,

programmable between 10 Hz and 100 Hz, the same as the

ADT7460. The default is 0, or HF PWM.

Bit 2 sets the direction for the GPIO: 0 = input, 1 = output.

Bit 3 sets the GPIO polarity: 0 = active low, 1 = active high.

Setting the Functionality of Pin 9

Pin 9 on the ADT7467 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

at Address 0x7D.

Table 4. Pin 9 Settings

Bit 1

Bit 0

Function

TACH4

THERM

SMBALERT

GPIO

RECOMMENDED IMPLEMENTATION

Configuring the ADT7467 as in Figure 15 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.

•

VCC measured internally through Pin 3.

•

CPU temperature measured using the Remote 1

temperature channel.

•

Ambient temperature measured through the Remote 2

temperature channel.

•

Bidirectional THERM pin. This feature allows Intel

Pentium 4 PROCHOT monitoring and can function as an

overtemperature THERM output. Alternatively, it can be

programmed as an SMBALERT system interrupt output.

CPU FAN

CPU

ICH

TACH2

PWM3

TACH3

D1+

D1–

GND

ADT7467

SCL

SDA

D2+

D2–

TACH1

PWM1

AMBIENT

TEMPERATURE

SMBALERT

THERM

PROCHOT

FRONT

CHASSIS

FAN

REAR

CHASSIS

FAN

Figure 15. ADT7467 Configuration

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