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TPS7A4501-SP: Managing thermal resistance

Joseph Wendt
Prodigy 240 points
Part Number: TPS7A4501-SP

Tool/software:

When looking at the RθJC(bot) Junction-to-case (bottom) thermal resistance and RθJB Junction-to-board thermal resistance for the TPS7A4501-SP, the RθJB is much higher. Can you please explain how RθJB differs from RθJC(bot)? And can the exposed thermal vias of the HKU package be soldered to the board to reduce RθJB or should a thermal epoxy be used?

  • 0
    TI__Genius 10970 points

    Hi Joseph,

    This document explains the thermal metrics thoroughly and should answer most of your questions.

    The thermal pad needs to have an electrical connection to GND, so I would recommend soldering it to the board.

    Thanks,

    Sarah

  • 0 in reply to Sarah Koch
    Prodigy 20 points

    Thanks Sarah,

    That is quite a comprehensive document.  I would usually want to solder the bottom thermal pad to GND.

    However in this case for the TPS7A4501-SP in the HKU package, Fig. 29 on page 21 shows he package elevated 0.022" above the PCB and no mention of soldering.    I can only imagine that since the part itself has internal vias, TI does not want to have those damaged in the soldering process to a PCB. We will have to perform our own lead forming and we will have to develop a non-solder,  Thermal Interface strategy.  It would be good to get the soldering profile information for theTPS7A4502-SP, HKU.   Thanks.

  • 0 in reply to Charles Masoomian
    TI__Genius 10970 points

    Hi Charles,

    We do provide general guidance on reflow profiles and other board assembly considerations for hermetic packages such as this one. 

    Soldering the thermal pad to the PCB is acceptable. This is what is done on the EVM for the device and also provides the necessary ground connection for the thermal pad.

    Thanks,

    Sarah