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TPS62260: why RθJC(top) is larger than RθJA?

Sherry Liang
Genius 10255 points
Part Number: TPS62260
Other Parts Discussed in Thread: TPS62080

Dear team,

In my understanding, RθJC(top)  should be smaller than RθJA, but below table is opposite, could you please help explain why RθJC(top) is larger than RθJA for this device?

Thanks & Best Regards,

Sherry

  • 0
    TI__Expert 7585 points

    Hi Sherry,

    Thanks for your question.

    Your understanding is correct, but TPS62260 datasheet has two values of  RθJC; RθJC(top) and RθJC(bottom), and RθJC(bottom) is much lower than RθJA.

    This is the reason why you have that RθJC(top) > RθJA.

    Please refer to Semiconductor and IC Package Thermal Metrics for further explanation.

    Thanks,

    Stefano

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml).

  • 0 in reply to Stefano Panaro
    TI__Genius 10255 points

    Hi Stefano,

    Thanks for your reply! But is is still strange that RθJA<RθJC(top) for WSON package while RθJA>RθJC(top) for SOT package. Is it possible that we make wrong position for these two package's RθJC(top)? 88.5 should be SOT package's RθJC(top) and 40.7 should be WSON package's RθJC(top).

    Thanks & Best Regards,

    Sherry

  • +1 in reply to Sherry Liang
    TI__Expert 7585 points

    Hi Sherry,

    Thanks again for the question.

    I don´t think that this should be the case: the WSON package can exploit the thermal pad to effectively dissipate the power to GND. Thus we usually have RθJA<RθJC(top).

    The SOT package doesn´t have this opportunity, thus is expected that RθJA is much higher than RθJC(top).

    I´ve checked some other devices (for example TPS62080) and it seems to be consistent for WSON package to have RθJA<RθJC(top).

    Thanks,

    Stefano

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml).