ST1S41 step-down switching regulator destroys itself on low impedance power source

TFrie.1 · ‎2021-05-11

Hi,

I installed 25 of the ST1S41 on a PCB and tested them with different Bench Power Supply and a electronic load or motors on the output. Everything worked very well till I swapped the Bench supply for a lithium Battery. Once I connected the Battery the switching regulator chips literally exploded. Has someone a explanation for that behavior and/or a solution for the problem?

Another Test I want to do but have not so far is to connect a little circuit between battery and converter that ramps the voltage up slowly (maybe 10ms).

Additional Info:

For the PCB Layout I followed the recommendations in the datasheet closely (see attached circuits and layout). There is a 100u capacity at input side of each converter and a 47u cap on output. The enable pin of the chip was pulled low when the battery had been connected. I was able to reproduce the behavior with one isolated chip (with only the necessary components connected)

Help and elucidation is much appreciated,

Best regards,

Tobias Friebel

LCE · ‎2023-06-23

Interesting test, did you find the cause of the problem?

Peter BENSCH · ‎2023-06-23

After a rough check of the layout, I could not find any noticeable errors.
I would be interested in the parameters of the bench supply and the lithium battery, i.e. voltage and internal resistance?

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