ADT7476AARQZ-REEL データシートの表示（PDF） - Analog Devices
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ADT7476AARQZ-REEL Datasheet PDF : 72 Pages
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ADT7476A
PRODUCT DESCRIPTION
The ADT7476A 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 ADT7476A 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 ADT7476A
AND ADT7468
• Dynamic TMIN , dynamic operating point, and associated
registers are no longer available in the ADT7476A. The
following related registers are gone:
o Calibration Control 1 (0x36)
o Calibration Control 2 (0x37)
o 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 ADT7476A).
• 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 ADT7476A.
• 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 ADT7476A does not support full shutdown mode.
• The ADT7476A offers increased temperature accuracy on
all temperature channels.
• The ADT7476A defaults to twos complement temperature
measurement mode.
• Some pins have swapped/added functions.
• The power-up routine for the ADT7476A is simplified.
• The ADT7476A 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 ADT7476A 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.
Rev. 0 | Page 10 of 72
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