LM2736: LM2736 failing - passing ~90 supply

Hi Barry,

I will need to find who can help look into the batch of ICs you are seeing the failures with. In the meantime I can help double check the design to see if there might be something else contributing to this. Can you share the schematic, layout and input voltage range?

Best Regards,
Anthony

Hi Barry,

You can report and return these parts for analysis at the link below.

www.ti.com/.../customer-returns.html

Best Regards,
Anthony

Good morning Anthony

Thank you for the prompt reply.

As motioned, we have been using the design before I started  at the company. The only addition to the original a year or so ago was the ferrites and TVS on the input.

Typically we use 12-14V input voltage, one product we do supply 18V. I expect ~5.6V out of the circuit.

With regards to returning components, we outsource the manufacture, I may be able to get a sample from them or we could send you a sample of populated PCBs. Would that be helpful at all.

Thank you again for your concern and help

Kind regards

Barry

Hi Barry,

Adding some ferrites to the input has potential to be related to this. Typically failures are due to over voltage stress on the IC and adding some inductance to the input could lead to some voltage spikes at the VIN pin of the IC. To prove or disprove this, it would be good to take some oscilloscope waveforms of the voltage at the VIN pin to make sure there isn't anything unusual there. I would try to take these waveforms in any scenario that there might be transients on input.

I think you may have tried to include a picture in your post and it didn't come through. Can you try again?

Below is a link to a document that I hope will help answer any question you have on returning parts. I do not personally deal with any of the returned parts until they are already back at TI. I think we would want you to send to us some fresh parts from the batch of suspect parts and some of the failed parts.

Best Regards,
Anthony

Good morning Anthony

Thanks for the document, I 'll read it shortly.

I did attempt to send you a copy of the schematic that we are using, I think it may not have passed through the various internet filters. I have placed it with in a word document and try to send it to you that way.

I was doing some 'scope checks on the supply to the PCB yesterday to see if I was getting any spikes before the PCB from the main supply, as we are regulating a 24V supply to 18V,  I have quite a large cap on the output of that main regulator, the rise time form 0 to max is around 20mS. There is no detectable overshoot there at least so I will look closer on the PCB itself now.

In most of our devices we normally use 12-14V supplied by a battery pack.

Thank you once again for your help

Kind regards

Barry