Creating a Split-Rail Power Supply With a Wide Input Buck Regulator

This application report demonstrates a unique method of generating a positive and negative output power supply using a standard buck regulator—one that maintains good regulation, has excellent cross regulation, and can regulate the positive output from a lower input voltage (i.e., boost). This document outlines a step-by-step method for designing the split rail power supply. The split rail power supply uses a wide input voltage step-down regulator as an inverting power supply to create the negative supply rail.