LM25085 Vout jumps on load

Hi Jerry,

It will be helpful to see the IOUT vs VOUT curve. Also is the switching behavior normal and consistent. This can be checked by looking at either the inductor current waveform or the SW node.

I have some scope image how do I post ?

Hi MAbie,

I think the "rich formatting" option allows you to attach files.

A1 is FB pin, A2 is PGATE

Hi Jerry,

I am not sure the scope shot tells me much. But I was reviewing the schematic, and it seems the output capacitor is really small. I suggest re-checking the component calculations with the quick-start calculator that is available on the LM5085 product folder under "tools and software" tab.

Another thing I noticed is that there is no CIN cap (small value) near the IC. I think the 47uF cap is good but there should be probably a ceramic cap close to the IC and the power stage.

Regards

Just to clarify the 3x series caps at the output amount to only 3.3uF.

Due to the lack of support I have chosen to use another buck converter from Maxim