ADT7476ARQH 查看數據表（PDF） - ON Semiconductor

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ADT7476ARQH

dBCOOL® Remote Thermal Controller and Voltage Monitor

ON Semiconductor 

ADT7476

Product Description

The ADT7476 is a complete thermal monitor and multiple

fan controller for any system requiring thermal monitoring

and cooling. The device communicates with the system via

a serial system management bus. The serial bus controller

has a serial data line for reading and writing addresses and

data (Pin 1), and an input line for the serial clock (Pin 2). All

control and programming functions for the ADT7476 are

performed over the serial bus. In addition, a pin can be

reconfigured as an SMBALERT output to signal

out−of−limit conditions.

Feature Comparisons Between ADT7476 and ADT7468

• Dynamic TMIN, dynamic operating point, and

associated registers are no longer available in the

ADT7476. The following related registers are gone:

• Calibration Control 1 (0x36)

• Calibration Control 2 (0x37)

• Operating Point (0x33, 0x34, and 0x35)

• Previously (in the ADT7468), TRANGE defined the slope

of the automatic fan control algorithm. TRANGE now

defines a true temperature range (in the ADT7476).

• Acoustic filtering is now assigned to temperature zones,

not to fans. Available smoothing times have been

increased for better acoustic performance.

• Temperature measurements are now made with two

switching currents instead of three. SRC is not available

in the ADT7476.

• High frequency PWM can now be enabled/disabled on

each PWM output individually.

• THERM can now be enabled/disabled on each

temperature channel individually.

• The ADT7476 does not support full shutdown mode.

• The ADT7476 offers increased temperature accuracy

on all temperature channels.

• The ADT7476 defaults to twos complement

temperature measurement mode.

• Some pins have swapped/added functions.

• The powerup routine for the ADT7476 is simplified.

• The ADT7476 has a higher maximum input voltage

TACH/PWM spec, supporting a wider range of fans.

• VCORE_LOW_ENABLE has been reallocated to Bit 7 of

Configuration Register 1 (0x40).

Recommended Implementation

Configuring the ADT7476 as shown in Figure 13 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 4.

• CPU temperature measured using Remote 1

temperature channel.

• Remote temperature zone measured through Remote 2

temperature channel.

• Local temperature zone measured through the internal

temperature channel.

• Bidirectional THERM pin. This feature allows Intel

Pentium 4 PROCHOT monitoring and can function as

an overtemperature THERM output. It can alternatively

be programmed as an SMBALERT system interrupt

output.

FRONT

CHASSIS

FAN

ADT7476

TACH2

PWM1

TACH1

REAR

CHASSIS

FAN

AMBIENT

TEMPERATURE

PWM3

TACH3 VID[0:4]/VID[0:5]

D2+

5(VRM9)/6(VRM10)

D2–

THERM

D1+

PROCHOT

D1–

VCC

SDA

+5VIN

SCL

+12VIN/VID5 SMBALERT

GND

Figure 13. ADT7476 Configuration

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