Understanding Power Impedance Supply for Optimum Decoupling

Noise in power supplies is not only caused by the power supply itself, but also the load’s interaction with the power supply (i.e. dynamic loads, switching, etc.). To lower load induced noise, most uninitiated designers use the biggest, lowest impedance capacitor that can be found, thinking that this will absorb the dynamic load current. This method is often hit and miss, and can even cause the power supply to oscillate and make the situation worse.