ADT7473ARQZ-RL7 ON Semiconductor, ADT7473ARQZ-RL7 Datasheet - Page 31

• Manufacturer Part Number: ADT7473ARQZ-RL7
• Description: IC REMOTE THERMAL CTLR 16QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7473ARQZ-RL7

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Fan Speed Counter, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 0.5 C
• Digital Output - Bus Interface: Serial (3-Wire, 4-Wire)
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

the system thermal characterization should also be involved
at the beginning of the process.
Automatic Fan Control Overview
speed of fans based on the measured temperature. This is
done independently of CPU intervention once initial
parameters are set up.
sensor and two remote temperature channels that can be
connected to a CPU on−chip thermal diode (available on
Intel Pentium class CPUs and other CPUs). These three
temperature channels can be used as the basis for automatic
fan speed control to drive fans using PWM.
optimizing fan speed according to accurately measured
temperature. Reducing fan speed can also decrease system
current consumption. The automatic fan speed control mode
is very flexible due to the number of programmable
parameters, including T
T
a given fan, are critical because they define the thermal
characteristics of the system. The thermal validation of the
RANGE
The mechanical or thermal engineer who is tasked with
The ADT7473/ADT7473−1 can automatically control the
The ADT7473/ADT7473−1 has a local temperature
Automatic fan speed control reduces acoustic noise by
values for a temperature channel and, therefore, for
REMOTE 1
REMOTE 2
LOCAL
TEMP
TEMP
TEMP
MIN
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
T
T
T
and T
MIN
MIN
MIN
RANGE
Figure 47. Automatic Fan Control Block Diagram
T
T
T
RANGE
RANGE
RANGE
. The T
100%
100%
100%
0%
0%
0%
MIN
http://onsemi.com
MUX
and
31
system is one of the most important steps in the design
process, so these values should be selected carefully.
control circuitry on the ADT7473/ADT7473−1. From a
systems−level perspective, up to three system temperatures
can be monitored and used to control three PWM outputs.
The three PWM outputs can be used to control up to four
fans. The ADT7473/ADT7473−1 allows the speed of four
fans to be monitored. Each temperature channel has a
thermal calibration block, allowing the designer to
individually configure the thermal characteristics of each
temperature channel. For example, a designer can decide to
run the CPU fan when CPU temperature increases above
60°C, and a chassis fan when the local temperature increases
above 45°C. At this stage, the designer has not assigned
these thermal calibration settings to a particular fan drive
(PWM) channel. The right side of Figure 47 shows controls
that are fan−specific. The designer has individual control
over parameters such as minimum PWM duty cycle, fan
speed failure thresholds, and even ramp control of the PWM
outputs. Automatic fan control, then, ultimately allows
graceful fan speed changes that are less perceptible to the
system user.
PWM
PWM
Figure 47 gives a top−level overview of the automatic fan
PWM
MIN
MIN
MIN
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
RAMP
RAMP
RAMP
AND 4
GENERATOR
GENERATOR
GENERATOR
CONFIG
CONFIG
CONFIG
PWM
PWM
PWM
PWM
PWM
PWM
PWM1
TACH1
PWM2
TACH2
TACH3
PWM3