MP4576 Fsw Above Output Capcitor SRF

DC-DC Power Converters
1

Hi,

I am designing 24V - 5V/0.4A buck converter using MP4576. In the MPS Design Tool, when the switching frequency is set to 1500MHz, one of the recommended output capacitors is GRM21BR60J226M. This capacitor has its SRF at around 1MHz. (Other recommended capacitors are similar). Above this value, the capacitance quickly peaks to 150uF, and then the impedance of the capacitor starts being represented by its inductance.

Is it safe to use the capacitor that holds its capacitance value only up to 900KHz or so when swithcing frequency is 1.5Mhz - 2Mhz, like in MP4576 regulator?

Thanks!

2

Hi denis.radoncic,

Thanks for posting on the MPSNow Forum.
I’d recommend choosing a capacitor that has a SRF above the switching frequency.
From a design perspective, I’d assume we want the capacitors to act like ideal circuit elements and not inductive.

Thanks,
Cindy