There are several recommendations for the LP2998 input power supply. An input capacitor is not required but is recommended for improved performance during large load transients to prevent the input rail from dropping. The input capacitor should be located as close as possible to the PVIN pin. Several recommendations exist dependent on the application required. A typical value recommended for AL electrolytic capacitors is 50 µF. Ceramic capacitors can also be used, a value in the range of 10 µF with X5R or better would be an ideal choice. The input capacitance can be reduced if the LP2998 is placed close to the bulk capacitance from the output of the 2.5 V DC-DC converter. If the two supply rails (AVIN and PVIN) are separated then the 47 uF capacitor should be placed as close to possible to the PVIN rail. An additional 0.1 uF ceramic capacitor can be placed on the AVIN rail to prevent excessive noise from coupling into the device.