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power dissipation of TPS65381

Jiaming Sun
Expert 1300 points

I use TPS65381 as power supply ,and I measure the current of each port of TPS65381

3.3V:80mA；

1.2V:57mA；

5V:115mA or maybe 130mA；

Under this situation,TPS65381 feels very hot,is it normal?and I find its thermal radiation makes components near it very hot too.How to make it cooler?

  • 0
    Expert 1300 points

    I already drew cooling area on the PCB ,but TPS65381 feels hot ,I want to know why?If its thermal Consumption is 600mW, is it sure to be hot with its small size?I want to get the answer of the ℃ of the TPS65381,based on calculation ;Is it calcuclated as 31℃/w × 0.6w =18℃ and its real  temperature is environment temperature( may be 23 ℃) + 18℃ =41℃;but I measure the highest temperature is 48℃.Does this because ventilation is not good?The TPS65381 will be used in a 3U cage,so the ventilation won't be very good ?Will TPS65381 work reliably?Reliability is very important for us.

     

  • 0 in reply to Jiaming Sun
    TI__Prodigy 710 points

    Thank you for using the Hercules forum. An engineer will soon be on the problem.

  • 0 in reply to Leo Huang1
    TI__Guru 68920 points

    Jiaming,

    31.4 C/W is the Theta-JA and from their datasheet it is specified on the High-K board.  That probably has thicker copper than you're using for starters.  And even then, that parameter is not really the right one to use.

    Please see the application report  http://www.ti.com/lit/an/spra953b/spra953b.pdf  for a good explanation of the thermal parameters and how to apply them to a system.   The Theta-JA parameter really is supposed to be used to compare one package to another but not to calculate the junction temperature of the part in absolute terms.  The app report explains how this use is a common mistake, and why it's not accurate.  The good news is I see that the TPS65381 datasheet has the other parameters listed like PsiJT and PsiJB and lots of footnotes about how the thermal simulations were made. 

    If you have more questions we should probably post them on the forum for the TPS65381.