Look at the burned LM2596

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Today, the company returned several devices for repair. All of them had LM2596 burnt out. This one was the worst.

This one is better

This one didn't get burned, but it just lost a leg.

Let's analyze the cause of the burnout. The chip is marked as National Semiconductor and the purchase price is more than 7 yuan, which seems to be true. The data on TI's official website states that the normal working voltage is 40V, and the working voltage is less than 28V, powered by a switching power supply. At first, another switching power supply was used, and the output was a little more than 24V. This problem occurred just after replacing a new switching power supply. The output of the new switching power supply is nominally 27.6V. The actual 27.7V is basically the same.
The equipment has been working normally with the previous power supply, but it doesn't work after replacing this power supply. They also returned two devices saying that they were hot when they were ready, but they didn't burn because they were powered off in time. However, I took the returned equipment and the returned switching power supply and tried it for an afternoon and didn't feel that the LM2596 was hot. It can be basically confirmed that there is no short circuit inside, because the equipment was not disassembled on site and the sealing was good. No debris will fall into it.
I suspect that they connected the wrong line when they replaced the switching power supply, but the equipment using this line was not completely damaged, but only a small part of it was damaged.

LM2596 is the same as the AMS1117 I mentioned a few days ago. Fakes are rampant. Will I be fooled again this time? Has the original model logo changed after National Semiconductor was acquired by TI? The chip is marked LM2596S-5.0 P+, and the National Semiconductor logo is in the upper left corner.

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