Hi all!
I'm using the LM25085 and the EVAL board and by using the Texas Webbench I have created a 5.0V output/0.5A buck converter with a 12V input.
As the attached oscilloscopes pictures (oscilloscope AC coupled) indicate there are very large (about 1.3Vpp) voltage spikes on the 5.0V output voltage. I have attached one zoomed out oscilloscope picture and a zoomed version in which the actual switch ringing can be seen. On the outzoomed picture the normal ripple can be seen together with a large 1Vpp voltage spikes that occue at every switch.
I have also attached the webbench report in which the schematic and BOM can be seen for the circuit. The only difference between this schematics and BOM and the real circuit on the eval board is the Cout capacitor that I hace chosen to 47uF with a 1ohm resistor in series to increase the ripple voltage.
Now, my question is what is causing the large voltage spikes/ringing on the output voltage that occurs at every switch and how to get rid of them. For the moment I'm not using any snubbers in my design but snubbers are not mentioned in either Texas webbench or the datasheet for this design so I recon they shouldn't be needed..
Is it caused by malfunctioning component or have I used a wrong components, or is PCB layout on the eval board not the best..?
/Ronny
