Hello, I am evaluating the MP100L for use in my system. I believe I followed the eval kit / typical app note circuit from the datasheet and I keep having my “fuse resistor” (20ohms, 1W) blow out. Sometimes it happens as soon as I plug it in and others it runs for a while and then blows. When it runs I get 12VDC on the output according to my multimeter, but when I look at it on an oscilloscope it has an oddly sinusoidal look to it with the negative voltages plunging very low. I’ve included a picture of my schematic for reference. As for the layout I believe I copied the eval kit the best I could. What could I be doing wrong?
I did find that I wasn’t using the same value for C11, I had 100uF, not 220uF…could this be causing the problem? Also, my R2 value is slightly different, I doubt this to be the problem but thought I’d point it out. One final question would be my “Fuse Resistor” is a 1W surface mount (2512 package) resistor instead of a through hole package; could this cause this kind of problem? Otherwise, everything is the same.
Replaced C11 with a 220uF Capacitor and this stabilized the 12VDC Output. Powering my device with an isolation transformer allows me to stop breaking the fuse resistor when measuring the output with my oscilloscope.