LM5164-Q1: Waveform and Schematics review - can not get a stable output

I am not sure how you selected your components.

Did you use Webench?

I would try Webench and/or use the calculator found on the product page.

Hi Frank. Thanks for your reply.

I use the Webench to calculate these elements's value.

I made two test board. Input voltage is 48V. One test board can output stable voltage (15V). Another cann't output stable voltage.

Looking at the Webench design, I find several differences between Webench and the schematic you show.

See attached.  The biggest difference is the output capacitance; it seems a little low in your schematic.

If you can check your design with the Webench (or calculator) components you may see a difference.

Also, be sure that you PCB layout is close to the recommend in the data sheet and/or Webench.

WBDesign381.pdf