LMR23630: External VOUT control method

Thank you for your advice.

Most of the boards pass the test, but some devices are broken.
So it seems that there is some deviation that causes the FB node to sink.
I would like to know the risks of sinking FB node.

Best Regards,

Hello, I will see if I can get a designer to comment on the risks. Allow me a couple days to follow up.

My colleague didn't see anything wrong with the implementation. I would advise we see if we can capture that failure again, while measuring the FB pin to ensure that the ABSMAX of the pin was not violated by the DAC.

Hi Marshall,

I would like to send the waveform in a private message.

Hello, you might be able to attached them to this thread in an excel sheet and then provide a password to the excel sheet over the messenger.  I dont think you can send files via the messenger.

I requested friendship, please accept it.

Hi Marshall,

Attached is the waveform when FB is shorted.
The operation is unstable and FB is shaking, but suddenly FB is shorted to GND and the output voltage rises.
The voltage on the FB pin does not exceed the rating.
What is the possible cause of the FB pin shorting?

Best Regards,

Hi, you could be potentially sinking or sourcing too much current out of the node. Potentially, you could try increasing the 10kOhm resistor to see if the behavior changes.

It also maybe that the wide vout range is causing issues for stability. You want to ensure that the output capacitance is designed for 1Vout and hopefully, the higher output voltages should be stable as well.

If you did overstress the device in past evaluation, you may want to consider changing out the device.