ASC7611 ETC2 [List of Unclassifed Manufacturers], ASC7611 Datasheet - Page 37

• Manufacturer Part Number: ASC7611
• Description: HARDWARE MONITOR WITH INTEGRATED FAN CONTROL
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

Thermal Considerations
The temperature of the aSC7611 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 Andigilog SMBus EVB provides a platform for
evaluation of the operational characteristics of the
aSC7511, aSC7512 and aSC7611. The board features a
graphical user interface (GUI) to control and monitor all
activities and readings of these parts. 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
© Andigilog, Inc. 2006
The power consumption of the aSC7611 is relatively low
6.
PC board leakage should be minimized by
maintaining minimum trace spacing and covering
traces over their full length with solder mask.
www.andigilog.com
- 37 -
BIOS code. After optimization, the settings may then be
programmed into the BIOS.
Features:
Application Diagram
The aSC7611 may be easily adapted to two-, three- or 4-
wire fans for precise, wider-range fan speed control when
compared to variable DC drive. Up to four fans may be
controlled. Fans 1 and 2 are independent. Fan 3 is
independent and may be tied to fan 4 for speed control.
Separate tachometer readings may be reported for all
four.
Application diagram in Figure 14 shows connections to
four 4-wire fans. External FETs may be added to the
PWM output to drive 3-wire fans.
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Interactive GUI for setting limits and operational
configuration
aSC7512 and aSC7611 Automatic Fan Control
Powered and operated from the USB port
Support for reading or writing to any register
User-defined, time-stamped logging of any
registers, saved in spreadsheet-compatible
format
Graphical readouts:
Selectable on-board 2N3904 or wired remote
diode
Headers for 2-, 3- and 4-wire fans with PWM
drive for aSC7512
Headers for up to 3 4-wire fans for aSC7611
Saving and recalling of full register set
configurations
LED indicators of alarm pin states
Optional use of external 12V fan power for
higher current fans
Optional connection to off-board SMBus clients
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Temperature and alarms
Fan RPM
Automatic fan control state
Voltage
October 2006 - 70A05007
aSC7611