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Board Level Hardware Description
1
Cooling Requirements
1-8
The Motorola MVME162LX Embedded Controller is designed and tested
to operate reliably with an incoming air temperature range of 0° to 55° C
(32° to 131° F). This is accomplished with forced air cooling at a velocity
typically achievable by a 100 CFM axial fan. Temperature qualification is
performed in a standard Motorola VME system chassis. 25 watt load
boards are inserted in two card slots (one on each side), adjacent to the
board under test, to simulate a high power density system configuration.
An assembly of three axial fans, rated at 100 CFM per fan, is placed
directly under the VME card cage. The incoming air temperature is
measured between the fan assembly and the card cage, where the incoming
airstream first encounters the controller under test. Test software is
executed as the controller is subjected to ambient temperature variations.
Case temperatures of critical, high power density integrated circuits are
monitored to ensure the component vendor's specifications are not
exceeded.
While the exact amount of air flow required for cooling depends on the
ambient air temperature and the type, number, and location of boards and
other heat sources; adequate cooling can usually be achieved with 10 CFM
and 490 LFM flowing over the controller. Less air flow is required to cool
the controller in environments having lower maximum ambient
temperatures. Under more favorable thermal conditions, it may be possible
to operate the controller reliably at higher than 55° C with increased air
flow. It is important to note that there are several factors (in addition to the
rated CFM of the fan), which determine the actual volume and speed of air
flowing over the controller.
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