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Tps7a4501 junction to case (top) temperature vs Power dissipation

swapna bramandlapally1
Prodigy 170 points

Hi,

I am working on Thermal characteristics of TPS7a4501.I calculated   junction to case (top and bottom) temperature using Theta jc(top) = Tj-Tc/Power dissipation and  Theta jc(bottom) = Tj-Tc/Power dissipation.

when power dissipation is increasing  junction to case ( bottom) temperature is also increasing linearly. but junction to case ( top) temperature is decreasing when power dissipation is increasing.Here i am just little bit confusing.

Please let me know if any consideration is missed.

Here i have attached table shows all temperature's readings. Highlighted with yellow color is junction to case temperature (top & bottom).

  • 0
    TI__Mastermind 41790 points

    Hi Swapna,

    This measurement is highly dependent on where the heat is transferred. ThetaJC top or bottom JEDEC standard assumes that almost all power of the LDO is dissipated to the top or bottom. This may or may not be the case in your test at different temperatures. Please see the below app note that describes this more in detail.

    http://www.ti.com/lit/an/spra953b/spra953b.pdf

    Regards,

    Darwin