EVAL-ADT7467EBZ ON Semiconductor, EVAL-ADT7467EBZ Datasheet - Page 35

• Manufacturer Part Number: EVAL-ADT7467EBZ
• Description: BOARD EVALUATION FOR ADT7467
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of EVAL-ADT7467EBZ

• Sensor Type: Temperature
• Sensing Range: -40°C ~ 120°C
• Interface: SMBus (2-Wire/I²C)
• Sensitivity: ±1.5°C
• Voltage - Supply: 3 V ~ 5.5 V
• Embedded: No
• Utilized Ic / Part: ADT7467
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AUTOMATIC FAN CONTROL OVERVIEW
The ADT7467 can automatically control the speed of fans based
on the measured temperature. This is done independently of
CPU intervention once initial parameters are set up.
The ADT7467 has a local temperature sensor and two remote
temperature channels that can be connected to a CPU on-chip
thermal diode (available on Intel Pentium class and other
CPUs). These three temperature channels can be used as the
basis for automatic fan speed control to drive fans using pulse-
width modulation (PWM).
Automatic fan speed control reduces acoustic noise by optimizing
fan speed according to accurately measured temperature.
Reducing fan speed can also decrease system current consump-
tion. The automatic fan speed control mode is very flexible due
to the number of programmable parameters, including T
T
and, therefore, for a given fan are critical because they define
the thermal characteristics of the system. Thermal validation of
the system is one of the most important steps in the design
process; therefore, these values should be selected carefully.
RANGE
. The T
MIN
and T
REMOTE 1
REMOTE 2
LOCAL
RANGE
TEMP
TEMP
TEMP
values for a temperature channel
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
T
T
T
MIN
MIN
MIN
T
T
T
RANGE
RANGE
RANGE
Figure 49. Automatic Fan Control Block Diagram
100%
100%
100%
0%
0%
0%
Rev. 3 | Page 35 of 77 | www.onsemi.com
MIN
MUX
and
PWM
PWM
PWM
Figure 49 shows a top-level overview of the automatic fan
control circuitry on the ADT7467. 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 ADT7467
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, one can decide to run the
CPU fan when CPU temperature increases above 60°C and to
run 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 49 shows controls that are fan-specific.
The designer can individually control parameters such as
minimum PWM duty cycle, fan speed failure thresholds, and
even ramp control of the PWM outputs. Therefore, automatic
fan control ultimately allows gracefully changing fan speed so
that it is less perceptible to the system user.
MIN
MIN
MIN
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
RAMP
RAMP
AND 4
RAMP
GENERATOR
GENERATOR
GENERATOR
CONFIG
CONFIG
CONFIG
PWM
PWM
PWM
PWM
PWM
PWM
PWM1
TACH1
PWM2
TACH2
TACH3
PWM3
ADT7467