Because the buck converter has a pulsating input current, a low ESR ceramic input capacitor is required for best input voltage filtering to minimize input voltage spikes. For most applications, a 4.7-µF input capacitor is sufficient. When operating from a high-impedance source (such as a coin cell), TI recommends a larger input buffer capacitor ≥10 µF to avoid voltage drops during start-up and load transients. The input capacitance can be increased without any limit for better input voltage filtering. The leakage current of the input capacitor adds to the overall current consumption.

Table 9-4 shows a selection of input and output capacitors.