Selection and Solution Guides

Application Notes

Quick Start Guide for a 0.5 Amp Buck Regulator Using The LM5574 and LM25574 (Rev. B)


The LM5574 and LM25574 switching regulators feature all of the functions necessary to implement an efficient high voltage buck regulator using a minimum of external components. These easy to use regulators include either a 42V (LM25574) or a 75V (LM5574) N-Channel buck switch with an output current capability of 0.5 Amps. The operating frequency is programmable from 50kHz up to 1MHz. Protection features include: current limit, thermal shutdown and remote shutdown capability. The device is available in a TSSOP-16 package. This step-by-step guide provides an easy to use process to quickly select the external components necessary to complete a design. More detailed information including theory of operation, design trade-offs and additional application guidance is available in the device datasheet. Shown below in Figure 1 is a complete schematic for a 0.5 Amp step-down DC-DC converter. Several external component values can be standardized for most applications. The input voltage range, output voltage and desired operating frequency dictate the remaining component values.