This slide shows what happens when a DC/DC converter that switches 180 degrees out of phase with another DC/DC Converter. The top 2 waveforms show 2 separate power stages switching at the same frequency. The input current is drawn at the same time, which yields an input current waveform shown in the 3rd waveform from the top as the sum of the power stages 1 and 2. If the Dc/Dc converters are synchronized to switch 180 degrees out of phase, the input current pulses occur at a different time interval as shown on the bottom waveform. This means that the power supply needs to be designed to handle the ripple of only one power supply resulting in less input capacitance. Therefore, capacitance cost and board space are saved.