For typical application, an input capacitor of 4.7µF is sufficient and recommended. A larger value reduces input current ripple further. The input capacitor buffers the input voltage for transient events and also decouples the converter from the supply. A low ESR ceramic capacitor is recommended for best filtering and should be placed between VIN and PGND as close as possible to those pins. In either case a minimum effective input capacitance of 3µF should be present.