8.2.2.1.2 Input Capacitor Selection

A ceramic input capacitor of 10 μF, 6.3 V is sufficient for most applications. Place the power input capacitor as close as possible to the VIN_Bx pin and PGND_Bx pin of the device. A larger value or higher voltage rating may be used to improve input voltage filtering. Use X7R or X5R types; do not use Y5V or F. DC bias characteristics of ceramic capacitors must be considered when selecting case sizes like 0402. Minimum effective input capacitance to ensure good performance is 1.9 μF per buck input at maximum input voltage DC bias including tolerances and over ambient temp range, assuming that there are at least 22 μF of additional capacitance common for all the power input pins on the system power rail. See Table 9.

The input filter capacitor supplies current to the high-side FET switch in the first half of each cycle and reduces voltage ripple imposed on the input power source. A ceramic capacitor's low equivalent series resistance (ESR) provides the best noise filtering of the input voltage spikes due to this rapidly changing current. Select an input filter capacitor with sufficient ripple current rating.

The VANA input is used to supply analog and digital circuits in the device. See recommended components from Table 10 for VANA input supply filtering.