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BCT-ETX-C3-XXX
S
INGLE
B
OARD
C
OMPUTER
I
NSTALLATION
Over-current detect input. Used to monitor the USB power over-current. Pull with open collector to GND if
over-current is detected.
C
OOLING
Efficient cooling is essential for long and reliable operation of any electronic equipment. The VIA C3 CPU
and the VIA VT8606 IC (commonly termed the 'North Bridge') do get hot in normal operation, and in an
elevated ambient temperature will require additional cooling. Cooling requirements will vary with
application, desired operating temperature, CPU load, memory size and board orientation.
Mounting the PCB vertically will aid natural convection and create a chimney effect. Passive heatsinks are
available for the CPU and the VT8606 IC. A fan, whilst not always desirable, will provide a high degree of
cooling even for a relatively slow airflow.
Further options that may be considered are sinking heat to the chassis or enclosure, and in extreme situations
the use of a heat pipe.
The CPU is equipped with an onboard thermal diode for temperature monitoring. This diode is connected to
a system monitor within the South Bridge. The South Bridge is fitted with a thermal monitoring device can
also monitor its own temperature. A thermistor is available to monitor the temperature of critical and
potential hot spots on the board. Temperatures can be monitored in the BIOS Set-up. If you wish to monitor
these temperatures from your application please contact the Blue Chip Technology Technical Support team.
When designing an enclosure, bear in mind that the greater the volume of air that can flow through the
enclosure, the greater the cooling effect and the lower the temperature rise above the ambient air
temperature. However, the volume produced by any fan will vary with the pressure against which it has to
work. The resistance to airflow (the back-pressure on the fan) will depend upon the enclosure, the mounting
and restrictions. Therefore, when mounting and cabling the board, it is essential that the free circulation of
the cooling airflow is not impeded.
The calculation of airflow through an enclosure is not straightforward, and depends on many factors. The
method of meeting the cooling requirements will be specific for each system. Consequently, the system
builder is responsible for ensuring adequate cooling. However, interpreting airflow volumes is not intuitive.
As an aid to selecting suitable cooling, the following example is offered. A 60 mm axial fan (such as a Papst
type 612NGH) blowing over the board can supply up to 46 m
3
/hour when unrestricted. Restrictions to the
airflow will reduce this volume.
C
ABLING
Whilst the BCT-ETX-C3-XXX does not have any cables it should be remembered that when integrating into
a system that careless routing of connecting cables could affect the cooling dramatically. It will also have a
bearing on EMC. Lengths should be limited to the necessary minimum.
Please note when interfacing into the IDE interfaces on your Host Board that to achieve higher IDE
throughput than UDMA33 requires the use of a special 80-conductor IDE cable or PCB tracking that mimics
this. Using a standard 40-conductor IDE cable or “one to one” PCB tracking will force the interface to work
at a lower speed.
All applications will require a power connection. The BCT-ETX-C3-XXX board requires a 5V, and if
necessary a 5 volt standby supply for ATX support. The power connection to BCT-ETX-C3-XXX is made
through the four ETX connectors.
Power wiring to the base board should be of an adequate gauge to ensure that the voltage does not fall below
the watchdog trip point (nominally 4.75V at the watchdog).
If a 5V standby supply is not available, the terminal should be linked to +5V supply. The Ethernet controller
and much of the power-sequencing blocks in the chipset are powered from this terminal.