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TPS7A4501-SP: HKU-10 thermal properties

Jussi Lehti
Prodigy 30 points
Part Number: TPS7A4501-SP

Hello,

Is there thermal metrics available for HKU-10 package when the thermal pad is not connected? We assume that the metrics given in the datasheet is applicable when the thermal pad is soldered and thus not applicable for our case. In our application the thermal pad will not be connected but it will be electrically connected via lid to ground.

  • 0
    TI__Genius 12150 points

    Hi Jussi,

    Yes, the thermal metrics for the HKU package likely apply only when the thermal pad is soldered. I will check with our thermal modeling team to confirm this is correct.

    The HKU is intended to be thermally connected to the board. Is there a reason for using the HKU package instead of the U package?

    Can you let us know how you intend to connect the device to the board (thermal conductive epoxy, air gap, or touching)? Having the thermal pad only touching the surface can be unpredictable. If the surfaces are not perfectly planar, airgaps will exist that significantly impact thermal transfer. Our thermal modeling team may be able to provide thermal metrics for your application if you can supply these details.

    Thanks,

    Sarah

  • 0 in reply to Sarah Koch
    Prodigy 30 points

    Hi Sarah,

    Thank you for the reply!

    The maximum current drawn is less than 80mA  and the maximum power dissipated in the component will be less than 270 mW. In that respect we could use U package which has the lower current rating but the RHA version is only available in HKU package. 

    In the planned assembly the thermal pad is intended to be left floating, so no direct contact to the PCB. The grounding of the pad and lid will be done externally.

    The PCB and the component will be in vacuum environment thus the heat flow from die is mainly via the pins of the package. How close the thermal metric values of U package would be to our application?

  • 0 in reply to Jussi Lehti
    TI__Guru 62930 points

    Hello Jussi,

    I support this product.  Sarah was helping out while I was OOO. 

    Since you have such a low power dissipation, it should not be an issue to have this thermally floating.  

    However, I would like to get our thermal modelling team to run a Psi Jb with it disconnected to get a ball park number on the thermal performance in this configuration. I suspect the Psi Jb will be similar to the U package.

    You can use the U value as an estimate until I can get the more accurate thermal model analyzed.  This may take up to 2 weeks, but I will see if I can get it quicker.

    Just a note: The seal ring/lid, and thermal pad of the HKU are electrically tied together in the package.   Thus, when you ground any one of these, the others will be tied to same potential.

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    TI__Guru 62930 points

    Jussi,

    Just wanted to let you know that the request for modelling is still in progress.

    Looking for results within one week.  Appreciate your patience.

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    TI__Guru 62930 points

    Jussi,

    I just received the thermal metrics without the thermal pad thermally connected to the board.

    Note: This is not the recommended attachment method.  However, this should not pose an issue if the lid is grounded and thermal relief is properly managed.

    Theta JA-High K :    100.3
    Theta JC, top :    29.6
    Theta JB :    80.3
    Psi JT :    17.0
    Psi JB :    75.0
    Theta JC, bottom :    20.4

    Based on Psi JB and your estimated max power dissipation, the Tj should only increase by less than 22C.

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

  • 0 in reply to Wade Vonbergen
    Prodigy 30 points

    Hello Wade,

    Thank you for the thermal metrics! We have now all information to continue.

  • 0 in reply to Jussi Lehti
    TI__Guru 62930 points

    Jussi,

    The thermal modelling engineer updated the results, as there was an error in one of the properties of the thermal pad.   The numbers did change, but not significantly.  I edited the results above.

    Pleas acknowledge back, so I know you received update.

    Regards,

    Wade