A Schottky is the preferred type for D1 diode due to its low forward voltage drop and small reverse recovery charge. Low reverse leakage current is important parameter when selecting the Schottky diode. The diode must be rated to handle the maximum output voltage plus any switching node ringing. Also, it must be able to handle the average output current. For the optimal performance, it is highly recommended to use a diode with a junction capacitance lower than 1 nF at 0 V.