Using a MP4569 at 50Vin, 5Vout, light load (50 mA Max), using a 33uH inductor, 47uF output cap. At light load of about 20mA, seeing roughly 70mV ripple. Can this be reduced, or inherent to this chip function? Thinking a smaller value inductor, like 18uH would offer some faster-reacting improvement in minimizing the ripple voltage. I did try raising the feedforward 39pF cap to 139 pF–with no effect.
Hi @nnovotney,
Are you testing this on our EVB or you have designed your own board? If yes, Can you share the schematic and layout?
A couple of things can be adopted in the design to reduce the ripple:
- Follow the PCB guidelines in the DS for optimal performance of the device. EVB is a good benchmark to start with.
- Use molded/shielded inductors. These can be found here.
- Try increasing the output caps. add 0.1uF to eliminate high frequency noise.
- Have FB trace away from the inductor, FB is the most sensitive trace.
Increasing the Cff will not help reduce output ripple. Cff helps in loop stability of the device.
I hope this helps
Saurabh