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LMR36015: High temperature in LMR36015

fabio ortolano
Intellectual 330 points
Part Number: LMR36015

Hello

I'm debugging a board with the power step-down LMR36015. Following the schematic that I used. I'm facing a strange high-temperature chip value even if without any load when I power the device with 40Vdc. the temperature rise up to 70 degrees. The output is stable. I also attach the signal on the inductor. What could be the reason?

  • 0
    TI__Mastermind 22301 points

    Fabio,

    It seems like there is not enough copper around your IC.

    See datasheet section 9.2.1.2.10 and Figure 19 about the importance of copper area around the IC for thermal dissipation.

    Also see the layout guidelines (11.2). The copper planes around the GNDs (pins 1, 6, 11) are important for heat sinking.

    Let me know if you have further questions,

    -Orlando 

  • 0 in reply to Orlando Murray
    Intellectual 330 points

    Hello

    thanks for the reply. As you could see I have not so much space around (in fact there are components on the other side and vias are reduced, I know). But thanks for the suggestion, if this is the solution I will investigate how to change this. For evaluate all the possibilities, could you reply me on these questions?

    - What if I lower the enable pin to 2V (when 40V)? Do this pin influence the heat?

    - What if I change the chip to one that is not FPWM? Could this change the situation?

    Thanks for these last suggestions.

  • 0 in reply to fabio ortolano
    TI__Mastermind 22301 points

    Fabio,

    - What if I lower the enable pin to 2V (when 40V)? Do this pin influence the heat?

    The Enable pin does not sink much current, is does not contribute to power loss.

    - What if I change the chip to one that is not FPWM? Could this change the situation?

    Absolutely. A FPWM converter will always be switching at full frequency, even at light load / no load.

    A converter using discontinuous conduction (DCM) would not be switching at light-load so would experience less heat rise at light load.

    Hope this heps,

    -Orlando

  • 0 in reply to Orlando Murray
    Intellectual 330 points

    Hello

    OK thanks, this last thing is very important.

    Thanks.