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LM5161: LM5161 sparks/burned during testing

Part Number: LM5161

Hello my friends.

Please help me. 

I used lm5161 to design a converter with input (15v-75v), output is 12V. After I assembled with my PCB, then I tested it. the sparks appeared among PIN 1,2 and PIN 3,4. After 30 second, LM5161 burned. 

I used 24VDC for input power. I tried 2 times with 2 PCB, but the result was the same. I sure that I have soldered the thermal pad using the hot air gun. I asked ST supporter by chat, they told to me as my schematic is correct. So, I dont know the reason for my problem.

I inserted my schematic, PCB in this post. Please find the cause for me. Thank you so much. 

  • Hello Vanquang,

    Were you able to capture waveforms during your testing before it was damaged? I would like to see VIN, VOUT, and SW.

    How much current is being drawn from your input supply during your start-up?

    Is any other circuitry populated on the PCB? 

    If this is a new PCB, it can be possible there is a short or issue with this layout?

    I do not see any obvious issues with your schematic?

    Regards, Jason

  • Hello Jason.

    Thank you for your reply

    • I did not capture waveforms during my testing. Maybe, in few days later, I will do again, and try to capture this information.
    • Input supply, I do not understand your question. But the input supply is 24VDC, and 3A.
    • I designed this PCB for BLDC motor controller. and LM5161 used to convert input (15v-75v) to 12V. And 12V will provide the voltage to microchip and driver gate.
    • In my PCB, I sure there is no short. Because, before I provide 24V of input supply, I checked the short of the PCB. But there was any short. 
    • Issue with the layout. I think there is no problem. But I will check again. 

    Do you have any idea for my problem?

    Best Regards and Keep safe. 

  • Hello Vanquang,

    Your schematic looks OK. It sounds like something is shorting on your board.

    Please monitor your input voltage and make sure the correct voltage is applied to the supply. 

    Please send waveforms when you are able.

    Regards, Jason

  • Hi Vanquang,

    I have not heard from you in a while. I hope that you have found the issue and it is working now.

    If I do not hear back soon, I will close the post. you can reply at any time to re-open.

    Regards, Jason