Electronic – Can there be “too much” capacitance on a buck regulator output


I've an MPM3610 buck regulator module with an integrated inductor of 0.47 µH and a fixed internal compensation. It employs constant-on-time regulation. The datasheet gives some application circuits with a ceramic input and output capacitors of only 10 µF.

According to common knowledge (which may be misleading..) more capacitance on the output will reduce output voltage ripple. However, I've no idea how the stability will be affected.

Since I've got quite some space left on my PCB I wonder how much extra capacitance I should reasonably add, taking into account the reduction of effective capacitance due to DC bias effects.

Best Answer

If you want to suppress the ripple more, you can add more output capacitance BUT don't place it directly in parallel with the 10uF output capacitor. Instead, make an LC filter so first through an inductor or a choke, after this you can add almost as much caps as you like. The extra inductor or choke will prevent the extra caps affecting the regulator's loop.

Like so:


simulate this circuit – Schematic created using CircuitLab