ASC7512 ETC2 [List of Unclassifed Manufacturers], ASC7512 Datasheet - Page 32

• Manufacturer Part Number: ASC7512
• Description: DIGITAL TEMPERATURE SENSOR WITH INTEGRATED FAN CONTROL
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

Thermal Considerations
The temperature of the aSC7512 will be close to that of
the PC board on which it is mounted. Conduction through
the leads is the primary path for heat flow. The reported
local sensor is very close to the circuit board temperature
and typically between the board and ambient.
In order to measure PC board temperature in an area of
interest, such as the area around the CPU where voltage
regulator components generate significant heat, a remote
diode-connected transistor should be used. A surface-
mount SOT-23 or SOT-223 is recommended. The small
size is advantageous in minimizing response time
because of its low thermal mass, but at the same time it
has low surface area and a high thermal resistance to
ambient air. A compromise must be achieved between
minimizing thermal mass and increasing the surface area
to lower the junction-to-ambient thermal resistance.
In order to sense temperature of air-flows near board-
mounted heat sources, such as memory modules, the
sensor should be mounted above the PC board. A TO-92
packaged transistor is recommended.
and should have little self-heating effect on the local
sensor reading. At the highest measurement rate the
dissipation is less than 2mW, resulting in only a few
tenths of a degree rise.
Evaluation Board
The aSC7511/aSC7512EVB provides a platform for
evaluation of the operational characteristics of the
aSC7511 and aSC7512. The board features a graphical
user interface (GUI) to control and monitor all activities
and readings of the aSC7511. The provided software will
run on a Windows XP™-based desktop or laptop PC with
a USB port.
In addition to being a self-contained fan speed control
demonstration, it may be connected into an operating
PC’s fan and CPU diode to evaluate various settings
under real operating conditions without the need to adjust
BIOS code. After optimization, the settings may be
programmed into the system.
Features:
© Andigilog, Inc. 2006
The power consumption of the aSC7512 is relatively low
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Interactive GUI for setting limits and operational
configuration
aSC7512 Automatic Fan Control
Powered and operated from the USB port
Graphical readouts:
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Temperature and alarms
Fan RPM
Automatic fan control state
www.andigilog.com
- 32 -
Application Diagrams
The aSC7512 may be easily adapted to two-, three- or 4-
wire fans for precise, wider-range fan speed control when
compared to variable DC drive. Pin 6 may optionally be
used as ALERT , pulled up to 3.3V with a 10K resistor to
warn the system of an extreme condition needing
immediate attention in any fan configuration.
12V
12V
5V
5V
5V
5V
10K
10K
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2-Wire Fan
2-Wire Fan
in Cooling
in Cooling
Module
Module
Figure 14 aSC7512 2-, 3- and 4-Wire Fan
4-Wire Fan
4-Wire Fan
in Cooling
in Cooling
Module
Module
3-Wire Fan
3-Wire Fan
in Cooling
in Cooling
Module
Module
Selectable on-board 2N3904 or wired remote
diode
Headers for 2-, 3- and 4-wire fans
Customizable Log file of readings
Saving of register setting configurations
LED indicator of pin state
Optional use of external 12V fan power for
higher current fans
Optional connection to off-board SMBus clients
or FDC637AN
or FDC637AN
or FDC637AN
or FDC637AN
15K
15K
NDT3055L
NDT3055L
NDT3055L
NDT3055L
5V
5V
5V
5V
5V
5V
10K
10K
10K
10K
10K
10K
7.5K
7.5K
Remote
Remote
Sensor
Sensor
Remote
Remote
Sensor
Sensor
Remote
Remote
Sensor
Sensor
CPU
CPU
CPU
CPU
CPU
CPU
Connections
1
1
2
2
3
3
4
4
1
1
1
2
2
2
3
3
3
4
4
4
1
1
1
2
2
2
3
3
3
4
4
4
VDD
VDD
VDD
VDD
VDD
VDD
PWM
PWM
PWM
PWM
PWM
PWM
D +
D +
D -
D -
D +
D +
D -
D -
D +
D +
D -
D -
aSC7512
aSC7512
aSC7512
aSC7512
aSC7512
aSC7512
August 2006 - 70A05003
SMBDAT
SMBDAT
SMBDAT
SMBDAT
SMBDAT
SMBDAT
SMBCLK
SMBCLK
SMBCLK
SMBCLK
SMBCLK
SMBCLK
TACH
TACH
TACH
TACH
TACH
TACH
GND
GND
GND
GND
GND
GND
aSC7512
8
8
8
7
7
7
6
6
6
5
5
5
8
8
8
7
7
7
6
6
6
5
5
5
8
8
8
7
7
7
6
6
6
5
5
5
2.2K
2.2K
2.2K
2.2K
2.2K
2.2K
Optional
ALERT
3.3V
3.3V
3.3V
3.3V
3.3V
3.3V
3.3V
3.3V
2.2K
2.2K
2.2K
2.2K
SMBCLK
SMBCLK
SMBDAT
SMBDAT
SMBCLK
SMBCLK
SMBDAT
SMBDAT
SMBCLK
SMBCLK
SMBDAT
SMBDAT
2.2K
2.2K
10K
10K
10K