SNVSB79A November 2018 – July 2019 LM25180
Select an input capacitance using Equation 24 to limit the ripple voltage amplitude to less than 5% of the input voltage when operating at nominal input voltage.
Substituting the input current at full load, switching frequency, peak primary current and peak-to-peak ripple specification gives CIN greater than 2 μF. Mindful of the voltage coefficient of ceramic capacitors, select a 10-µF, 50-V ceramic input capacitor with X7R dielectric in 1210 case size. Equation 25 gives the input capacitor RMS ripple current.