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I have recently designed a PCB with a buck converter based on the LM3671 buck converter IC from TI to step down 5V to 3.3V. However, there is ringing on the rising and falling edges, and after a short amount of time the buck converter failed. It melted the solder on its solder pads and the internal MOSFET seems to have failed short. The oscilloscope trace that I was able to get before it failed looked like this: Oscilloscope trace (Sorry for the poor image quality) I used the reference design from the datasheet for my schematic: Schematic I tried to follow the best practice guidelines from several documents, including the datasheet for the LM3671 for the PCB layout: PCB layout I'm assuming I screwed up the PCB layout and added in some parasitic components somewhere which are causing the ringing on the rising and falling edges, but I'm not sure. It might also just be thermal design or something else. I'm just wondering why the buck converter failed, and what changes I can make to correct the issues that caused the IC to fail. Sorry if this is a dumb question. This is my first buck converter design and I'm just trying to figure stuff out.

Edit for some more details: The maximum load current that I have is about 500ma with the average load current being well below 200ma. I am using this(MAMK2520T2R2M ) inductor.

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  • \$\begingroup\$ What load current are you using and what is the inductor (link to device)? \$\endgroup\$ – Andy aka Apr 27 at 9:35
  • \$\begingroup\$ @Andyaka I added in the details that you requested into the question. \$\endgroup\$ – Aiden Grossman Apr 27 at 17:57
  • \$\begingroup\$ The inductor is OK. On your top picture of the o-scope - those wires that can be seen coming from what looks like a power supply - are they the power feeding wires to the circuit board? \$\endgroup\$ – Andy aka Apr 27 at 18:03
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I think you need to have protection on your incoming power pins on the chip. The absolute maximum rating for the device is 6 volts and I see evidence that this has been exceeded. This is due to wiring problems. If you want to use it like this then you should use a 5.6 volt zener on the Vin supply pins: -

enter image description here

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  • \$\begingroup\$ Thank you for your answer. I'll certainly have to do more investigation in relation to the input voltage. I was using the USB port that I have on the board, but I was powering it from my laptop and there might have been some large voltage ripple or something that caused the voltage to rise high enough to kill the IC with the back EMF or something like that. \$\endgroup\$ – Aiden Grossman Apr 27 at 19:36
  • \$\begingroup\$ It would be the bookmaker’s odds on favourite because Iran will be vulnerable on the input voltage. \$\endgroup\$ – Andy aka Apr 27 at 20:02
  • \$\begingroup\$ Did part of that message get auto corrected? \$\endgroup\$ – Aiden Grossman Apr 27 at 20:07
  • \$\begingroup\$ I meant to say "It would be the bookmaker’s odds on favourite because Vin will be vulnerable on the input voltage." God knows how it got turned to Iran LOL. \$\endgroup\$ – Andy aka Apr 28 at 7:39

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