Design Trends and Perspectives of Digital Low Dropout Voltage Regulators for Low Voltage Mobile Applications: A Review

Low-dropout (LDO) voltage regulator has fascinated industry professionals and academia for the past few decades, and this trend is expected to continue in the coming years. The high demand for a stable linear regulator architecture that performs well in systems-on-chip (SoC) power management integrated circuits (PMICs) is a key factor driving innovation with different complementary metal-oxide-semiconductor (CMOS) technologies. Yet, there are several performance parameter trade-offs to be considered, such as transient response, output ripple, area, power efficiency, supply voltage range, and current efficiency in the current LDO design architecture. All these parameter trade-offs become more severe during the back-end CMOS processes with additional limitations, for example, channel length modulation, stress sensitivity, and power leakage, among others. Therefore, this paper presents an overview and comparison of various digital LDO (DLDO) topologies, functionalities, and performance specifications, which can serve as a virtual study or reference for others.