The next step after this is to pick the input capacitor and output capacitor to meet the requirements. Note the assumed 120 mΩ ESR. Here, the designer can use KEMET’s different capacitor technologies to accommodate the design requirements. On a switching regulator's output, different capacitor technologies will change the amount of ripple voltage based on the ESR and ESL, as shown in the graph. Having multiple capacitors in parallel will improve the combined impedance effect over frequency. It is often a design requirement to maintain a certain impedance level over a particular frequency band to ensure that it can cover all the required transients. The graph from KEMET’s capacitor simulation tool K-SIM shows a plot of the combined impedance of one 0201 capacitor, two 0402s, two 0603s, and a KO-CAP®. The network of caps maintains an impedance below 100 mΩ from about 100 kHz up to 70 MHz. From here, the designer can examine the effect of the combined impedance and ESR across frequency. Apart from impedance, there are other cap characteristics the designer needs to consider when selecting the filtering caps. When selecting MLCC class 2 and 3 dielectrics like X7R and X5R, the designer has to look into DC bias and aging factor. The Class 1 (C0G and U2J) or higher density technology like KEMET’s KO-CAP do not have DC bias and aging (volumetric efficiency).