Manufactured with BiCDMOS process, BD9E300EFJ-LB single-channel synchronous rectification step-down DC/DC converter features 40 V withstand voltage input with built-in power MOSFET for switching and output current of 2.5 A. Adoption of N-channel MOSFET at upper and lower sides promotes efficiency, and diode necessary for bootstrap for producing gate drive of upper-side N-channel MOSFET is also built in. Acceleration of switching action to 1 MHz enables use of compact inductor and capacitor.