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TPS54335A: Rtheta j-a, Rtheta-Jc(top)

KANJI SHIBATANI
Mastermind 6205 points
Part Number: TPS54335A
Other Parts Discussed in Thread: TPS54332

Hello

Would you please let us know test condition about Rtheta j-a and Rtheta-jc(TOP)?

( Is is this conditon means: thermal pad is soldered???)

I don't know why Rtheta j-a :43.0 deg-c/w is lowerer than R theta-j-c(top): 55.4 deg-c/w  .

My understanding is  most of Rtheta j-a  is higher than theta_jc, but why Rtheta j-a is lower than Rtheta j-c(top)?

Would you please adivse but  such a basic question ?

Best Reagrds

  • 0
    TI__Genius 10070 points
    Hi,

    Yes, there is thermal pad.
    www.ti.com/.../spra953c.pdf

    Shawn
  • 0 in reply to Shawn Nie
    Mastermind 6205 points

    Dear Shawan-san


    Thank you you for your reply immediately!

    But please let me advise again.


    Q1  

    I know TPS54335A has power(thermal ) pad. My question is different.

    For Rtheta-ja  43.9 deg-C (10 VSON) testing, power pad is mounted to PCB? 

    Otherwise  just 10 pins are soldered to PCB?

    Which is correct?


    spra953c.pdf page 2

    >Step 1. A device, usually an integrated circuit (IC) package containing a thermal test chip that can both dissipate power and

    >measure the maximum chip temperature, is mounted on a test board.


    Q2


    From TPS54335A TI Webench simulation, " Rtheta ja effective "  is  34 deg-C/W.

    I think " Rtheta-ja effective"  case, power pad is soldered to PCB , and customer prefer to use this for their design.

    Is it correct?

    Iwebench.ti.com/.../15

    Best Regards

  • 0 in reply to KANJI SHIBATANI
    TI__Genius 10070 points
    Hi,

    Please see my input:

    Q1:
    The thermal pad is mounted to PCB. You can check other part, such as TPS54332 which has thermal pad, Rtheta-ja is lower than Rtheta-jc.

    Q2:
    Rtheta-ja which is provided in the datasheet is simulated with a standard method and board, it is only for comparison with other package.
    For the " Rtheta ja effective is 34 deg-C/W", I think it was measured with EVM. Of cause, most of the customer will use the thermal pad, it is useful for improving the heat dissipation capacity.

    Shawn
  • 0 in reply to Shawn Nie
    Mastermind 6205 points

    Dear Shawn-san

    Thank you for your answer so quickly!

    Thank you again