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I need to step down 24V to 5V in one of my projects, so I used TPS54302DDCR (has a maximum input voltage of 28V) by TI and designed the circuit according to its datasheet and example schematic. However when it has been powered up, it will either work, or it will burst into flame. However I tried powering at 12V and it had no problem at all. So I wonder if it is because the input voltage rippled when powering up and exceeds the maximum input of the buck converter, resulting in an internal breakdown that created a short, so it burns? Does a big capacitor on the input side solve this problem? Is there a recommended value? Or I need to add some more components? Here is the circuit I am using: enter image description here

EDIT: Here is the image of the board layout (I already added a 470uF cap on the input side), I tried my best to stick to the layout recommendation from the datasheet.

enter image description here enter image description here

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  • \$\begingroup\$ Comments are not for extended discussion; this conversation has been moved to chat. \$\endgroup\$ – Voltage Spike Sep 2 '20 at 4:37
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Add huge capacitors to the input side seems to solve the problem. I tried a single 35V 470uF electrolytic capacitor and it seems to solve my problem immidiately. I am looking into step up to 1000uF in my final design if applicable.

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  • \$\begingroup\$ That means the problem was the inductance on the wires/traces between your power source and buck input was too high so whenever the current was interrupted, the inductance produced a voltage that stacked on top of your power source voltage which then exceeded your buck input. How long were the wires? \$\endgroup\$ – DKNguyen Sep 15 '20 at 21:02
  • \$\begingroup\$ @DKNguyen It's about 1 meter long. Someone in the chat also mentioned wire inductance, and I have no idea about that. Do I need to tweak other things? \$\endgroup\$ – whc2001 Sep 15 '20 at 21:12
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    \$\begingroup\$ 1 meter would definitely have enough inductance to do it. No need to tweak if you threw caps on. It sounds like you do not understand what decoupling caps are for. If you read up on it and understand it then you will understand why 1 meter of wire at 100kHz frequencies are a problem. \$\endgroup\$ – DKNguyen Sep 15 '20 at 21:13
  • \$\begingroup\$ @DKNguyen Under my impression the big electrolytic caps are used to dampen the sudden change of the voltage, and smaller ceramic caps to suppress potential high-frequency noises. I will definitely look into details about decoupling capacitors later. \$\endgroup\$ – whc2001 Sep 15 '20 at 21:22
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    \$\begingroup\$ They don't just serve one role in the same part of the circuit. \$\endgroup\$ – DKNguyen Sep 15 '20 at 22:59

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