9.2.2.3 Input Capacitor Selection

Because of the nature of the buck converter having a pulsating input current, a low-ESR input capacitor is required for best input-voltage filtering and minimizing the interference with other circuits caused by high input-voltage spikes. Each DC-DC converter requires a 10-μF ceramic input capacitor on its input pin VINDCDCx. The input capacitor is increased without any limit for better input-voltage filtering. The VCC pin is separated from the input for the DC-DC converters. A filter resistor of up to 10R and a 1-μF capacitor are used for decoupling the VCC pin from switching noise. Note that the filter resistor may affect the UVLO threshold, because up to 3 mA can flow through this resistor into the VCC pin when all converters are running in PWM mode.