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Original question:

LM3150: Excessive heat in Mosfets

LM3150: Excessive heating ic when input give to 25 to 28 V thats time output will change

hardik jani
Prodigy 150 points
Part Number: LM3150

Hello Sir

I have to work in LM3150 switcher please find below issues are facing

When giving an input voltage is 24 V that's time IC working fine we get proper output continues 5V

but give input gather then 24 V  means 27 to 29 V that's time IC had heating, as well as the output voltage, is change  5 V to 6 V not stable

Please give some solution regarding this issue

as well as I have attached my schematic picture.

Best regards

Hardik Jani

  • 0
    TI__Mastermind 25590 points
    Hardik,

    1. The device may be unstable. Check the SW node and make sure it's a stable rectangular wave. Check at 24VIN, 5VOUT, then check at other conditions.

    2. The layout may not allow for proper heat dissipation. Please share the layout. And what's your IOUT?

    3. Something may be breaking. The FETs you are using are rated for 30V. You are applying an input voltage up to 29V which does not leave enough margin, especially if the SW node is ringing. Check to make sure you are not exceeding the abs. max rating specs of the IC and other components.

    -Sam
  • 0 in reply to Samuel Jaffe
    Prodigy 150 points

    Hello  Samuel,

    Thank you so much for your reply

    Please see below my layout picture

     please see the layout  and give your valuable input

    2. The layout may not allow for proper heat dissipation. Please share the layout. And what's your IOUT?

    Ans:-my IOUT is 5A

    3. Something may be breaking. The FETs you are using are rated for 30V. You are applying an input voltage up to 29V which does not leave enough margin, especially if the SW node is ringing. Check to make sure you are not exceeding the abs. max rating specs of the IC and other components.

    Ans:- yes you are right we have 30 A FET select but we give max 27 V so please give the solution regarding this issue

    Thank you for advance

  • 0 in reply to hardik jani
    TI__Mastermind 25590 points
    Hardik,

    The thermal pad under the IC should be connected to a large GND plane. I see the thermal pad is cut between the pad copper and the GND plane. This should be connected to allow the heat to escape.

    C2 and C3 are very far from Q1 and Q2. This will create inductance in that current loop which will cause ringing/overshoot. I think you should have higher voltage FETs for more margin anyway but definitely in this case.

    The layout appears to separate the PGNDs from the SGNDs and the SGNDs from each other. Poor GNDing layout can cause instability regardless of the schematic. Please check the datasheet and EVM for more layout guidelines for GNDing as well as general layout.

    I believe your issue lies in layout. You should try to narrow down the issue (instability (due to what?), overshoot, and/or thermal pad). Then follow the guidelines on your next layout revision.

    -Sam