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TPS56628: Thermal information

Liston D Souza
Prodigy 200 points

Part Number: TPS56628

Tool/software:

Dear Team,

As per the datasheet, Junction to Ambient Thermal Resistance (θja) = 43.5 °C/W whereas Junction to Case Thermal Resistance (θjc) = 49.4(°C/W)
To calculate Case to Ambient Thermal Resistance (θca) = θja - θjc will be a negative value.

Is the data available in the datasheet valid?

Regards,
Liston

  • 0
    TI__Genius 13245 points

    Hi Liston,

    A response will be posted this week.

    Thanks,

    Calan

  • 0
    TI__Mastermind 27670 points

    Hi Liston,

    Here is what I got from our thermal packaging team:

    This happens occasionally as the tests are separate and unrelated.  Theta-JA assumes a natural convection environment with a 4 layer PCB, so most of the heat is dissipated through the exposed pad and into the board.  Theta-JC (Top) assumes a 1 layer PCB with an infinite heat sink on top of the package designed to force all of the heat to the top of the package. 

     The DDA package is not optimized for top side cooling so Theta-JC (Top) is quite high.  The formula to calculate case-to-ambient thermal resistance is not valid since the tests use different conditions.

    Hope this helps.

    Thanks,

    Amod