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Thermal/Airflow question

Titusc
Intellectual 660 points


Hi there,

I am new to thermal.

I want to ensure my SUT will still operate with a fixed temperature without airflow.  I placed my SUT in the temperature chamber.  What can you say about the airflow?  The fan turns on and off constantly to regulate the temperature.

Any input?

Thanks,
TC

  • 0
    TI__Guru**** 191445 points

    To assist in answering your question, you should always post the IC number in the tile of you post.  Also you should describe in detail your input voltage, output voltage and load current.  Any other information you can include will be useful as well.

  • 0
    TI__Expert 4350 points

    TC,

    I don't have the details of your system, but in general, your chamber needs to be set up to emulate the real end system environment. If your design is not shielded from the airflow in the chamber, then the test is not representative. One option would be to place your design inside some sort of enclosure (like a cardboard box, or the box in which the SUT is normally shipped), and place that box in the chamber. You will need to have some holes in the box so that the controlled chamber temp reaches inside the box, but small enough holes (and few enough) so that the chamber airflow does not grossly affect the results. It is a fine line between enough holes to get thermal equilibrium and not so many that the results get skewed. You really want to set it up to emulate the real system.

    Another option would be to perform the test on the bench top with an appropriate amount of free space (and airflow or deliberately no airflow, whatever is representative), and extrapolate the results linearly. This might be good enough, unless you are specifically looking for the effects of actual elevated temperature (like a temperature activated fan kicking in, or the drift of parameters with temperature). But if you are looking for relative delta-T, it might be good enough. Plus this gives you the option to use an IR camera.

    MC.