In a DC application, when the switch is on, the current will flow from Vin to Vout, and ideally Vout is equal to Vin. However, in reality this is not possible. Vout will be lower than Vin due to the voltage drop from the switch. In order to make this more ideal, a low Rds(on) switch is required to achieve this. The lower the Rds(on) that the switch MOSFET has, the less voltage drop in between Vin and Vout. Low Rds(on) is very crucial in this type of applications, and Infineon has the right devices for this type of application.