I didn´t expect to be having issues with a buck converter, but here I am. My design goal is a simple 15-60 V to 10 V buck converter. I settled with the following schmematic:
I designed a 2-layer board with copper pours on both layers with stitching vias:
(Ignore the terrible soldering)
During testing, I made temporary changes to component values:
Input capacitance: 11 μF,
Output capacitance: 10 μF,
Feedback resistors: 9.1 kΩ and 1.3 kΩ
I tested the converter with an input voltage of 25 V from a fairly noisy bench supply. I loaded the 10 V rail with 120 Ω. Here are the results:
Vout = 5.05 V instead of ~10 V, Vfb = 0.63 V instead of ~1.22 V according to the datasheet.
"AC" results (with bad oscilloscope probing):
Data measured after changing inductor from 22 μF to 100 μF:
Weird switch node voltage:
I know that the layout and component selection is not optimal, but I think this should only explain high ripple, low efficiency, etc. but not such a massive regulation issue.