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TPS51200: The question about Thermal Information

user5795039
Prodigy 190 points
Part Number: TPS51200

Dear all.

In the datasheet of TPS51200, the Thermal Information told us that "Rja " is less than "Rjc", but genarally,in my opinion, I think normally Rja " should be laeger than "Rjc". So I want to know that why the "Rja " is less than "Rjc" in this datasheet?

best regards.

  • 0
    TI__Mastermind 24075 points
    Hello,

    In most cases RθJA does have the highest value, but the situation that Rjc is higher than Rja does happen sometimes and is not an anomaly. It is because of the different environmental and boundary conditions used for these metrics. The Theta-JA scenario uses a 4-layer PCB with thermal vias and a natural convection environment where the heat is able to take multiple paths and most of the heat flows into the PCB. The Theta-JC (top) scenario uses a single layer PCB with no vias and places a large heat sink on top of the package to force all of the heat in that direction, causing the difference between the junction and case temperatures to be very high on some packages.

    Thanks
    Qian