ZHCSNT4I February 2006 – May 2021 LM5009
PRODUCTION DATA
D1: The important parameters are reverse recovery time and forward voltage. Reverse recovery time determines how long the reverse current surge lasts each time that the buck switch is turned on. The forward voltage drop is significant in the event that the output is short-circuited because only this diode voltage forces the inductor current to reduce during the forced off-time. For this reason, a higher voltage is better, although higher voltages affect efficiency. A good choice is an ultrafast or Schottky diode with a reverse recovery time of approximately 30 ns and a forward voltage drop of approximately 0.7 V. Other types of diodes can have a lower forward voltage drop, but can also have longer recovery times or greater reverse leakage. The D1 reverse voltage rating must be at least as great as the maximum VIN, and the D1 current rating must be greater than the maximum current limit threshold (370 mA).