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TPS7H1101A-SP: Package thermal properties

Jill Burnham
Prodigy 30 points
Part Number: TPS7H1101A-SP

If the thermal pad of the HKR package is not soldered to the PCB, what is the R-theta-J-B ?    Our power is quite low.   We'd like to calculate the junction temperature assuming only conduction through the leads of the package (in a vacuum).    Thanks.

  • 0
    TI__Guru 62930 points

    Jill,

    I can possibly have this situation modeled.

    Are you indicating there is a gap between the thermal pad and the board?   In a vacuum?  

    I will request this, and get back with you if more information is needed.

    With the holidays, and effort required for this task, it could take a little time.

    Can you provide details regarding Vout, Vin, max current?

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    TI__Guru 62930 points

    Jill,

    Our modelling team was able to generate this fairly quickly.

    Using only leads for thermal relief:

    Theta JB 34.6

    Psi JB 31.6

    If this answers your question, please click "This Resolved My Issue"
    Regards,
    Wade

  • 0 in reply to Wade Vonbergen
    Prodigy 30 points

    Thank you for the quick reply.   Could you confirm that the Psi JB value posted is in vacuum and does not include convection ?

  • +1 in reply to Jill Burnham
    TI__Guru 62930 points

    Jill,

    I checked with the modeler, and he indicated that it is not modeled as a vacuum, but with an air gap.  

    It was believed that nearly 100% heat transfer would be through leads in this configuration.  However, he did experiment to confirm using larger gap and longer leads.  The metrics increased by larger than expected.

    Can you estimate the gap that will be present between thermal pad and board? 

    I have asked if it is possible to model the gap as vacuum.

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    TI__Guru 62930 points

    Jill,

    We were able to simulate this without convection.  Only conduction and radiation is modeled.

    Under these conditions.  Psi JB is 69.3, and Theta JB is 78.2

    If this answers your question, please click "This Resolved My Issue"
    Regards,
    Wade