This document provides a design workflow for a step-down DC-DC converter using the NJM2309 PWM controller IC. The workflow includes: [1] setting the controller parameters; [2] selecting resistor values for the output voltage; [3] choosing the inductor and capacitor values; [4] adding compensation to stabilize the converter; and [5] simulating the load transient response. Appendices provide additional details on compensation calculation and feedback loop types.