Design considerations for VRM transient response based on the output impedance

Abstract

This paper discusses the transient response of voltage regulator modules (VRMs) based on small-signal models. The concept of constant resistive output impedance design for the VRM is proposed, and its limitation in application is analyzed. The impact of the output filter and the feedback control bandwidth shows that there is an optimum design for the VRM to achieve fast transient response, small size and good efficiency. Simulations and experimental results prove the theoretical analysis.