L5988D Switching Regulator The STMicroelectronics L5988D fully integrated switching regulator is designed for consumer, networking, computer peripherals, industrial, and factory automation applications. The STMicroelectronics L5988D features synchronous rectification that eliminates an external diode, providing high efficiency and space savings. The switching frequency of the L5988D is fixed at 400kHz fixed or programmable up to 1MHz for further reduction of the overall board size.