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My query is reg the TPS54360 , Thermal Resistance

Varunesh Kumar
Intellectual 930 points
Other Parts Discussed in Thread: TPS54360, LMR14020

My query is reg the TPS54360 ; its Thermal Resistance . The Data Sheet mentions it as 42.0*C/W for Std Board ; while Webench takes is as ICTheta JA Effective as 26DegC/W . Which is correct ? Regards

  • 0
    TI__Guru**** 191445 points
    The datasheet value of 42 C/W is based on the JEDEC standard coupon. It is generally used for comparison purposes only. The actual theta J-A will depend greatly upon your actual PCB design.

    I ran the default webench design. The Op Vals does return 1.06 W power dissipation, 57.5 C junction temperature and effective theta J-A of 26 C/W. I do not know where that came from. I also ran the webtherm simulation. It returns the same 1.06 W power dissipation, but 74.4 C junction temp and the theta J-A is 41.9 C/W, which is very close to the datasheet value. I suspect the 26 C/W value is an error. I will report it to the WB team.
  • 0 in reply to JohnTucker
    TI__Mastermind 35165 points

    The 26 C/W comes from measurements on the EVM in open air. We decided to use this value because typically if we use the JEDEC standard coupon value it is very pessimistic when compared to the real performance. The thermal simulation will match this value much better if you change the edges of the PCB from insulated to open air 30 deg C. The TJA decreases to 31.7 deg C/W.

    However like John said performance depends greatly on the actual PCB design and ambient conditions in the application.

  • 0 in reply to Anthony F
    Intellectual 930 points

    Thanks to Anthony and John for the quick response.

    Does that ( lower R-theta ) hold for other similar devices like LMR14020 ?

    Rgds