Optimizing Buck Converter Transient Response: ESR Considerations and Loop Design

As the magnitude and slew rate of digital-load current continue to increase, peak output-voltage deviation, recovery time, and stability with low-equivalent-series-resistance (ESR) ceramic capacitors have become central concerns in the design of DC-DC buck converters. This review adopts transientdetection delay, power-stage current-slew capability, and feedback-signal quality as a unified analytical framework to compare hysteretic control, constant-on-time (COT) control, V 2 control, and their voltage-, inductor-current-, and capacitor-current-feedback variants. In addition to examining insufficient ripple, phase lag, and subharmonic-oscillation mechanisms under low-ESR conditions, the review evaluates the benefits of virtual-ripple injection, adaptive boundaries, frequency locking, DCoffset cancellation, and auxiliary-current injection in terms of peak voltage deviation, recovery time, switching-frequency stability, and DC regulation accuracy. Engineering factors that have received comparatively limited attention in earlier reviews are also considered, including the die-area, quiescent-power, calibration-complexity, and light-load-efficiency penalties associated with sensors, error amplifiers, phase-locked loops (PLLs), digital logic, and auxiliary power stages. Multiphase and digital/hybrid ripple-control techniques are further discussed. Finally, architecture-level comparison matrices and representative measured silicon results are used to provide design guidance for controlarchitecture selection under different load-current levels, frequency constraints, and low-ESR operating conditions.