A 0.6-to-1.1-V 2-A Dead-Zone-Based Dual-Loop Ring-Amplifier LDO for High-Current-Density Custom HBM Applications

This letter presents a ring-amplifier low- dropout regulator (RA-LDO) that delivers a heavy load current of up to 2 A and achieves an ultrafast transient response across a wide input voltage range from 0.6 to 1.1 V. The RA-LDO employs a coarse-fine dual-loop regulation scheme, combining a high-slew-rate coarse ring-amplifier (RA) with a high-gain fine RA to enable both fast transient response and accurate output regulation. A dead-zone–based dual-loop control mechanism is adopted to ensure stable operation by leveraging the inherent dead zones of RAs. To improve power efficiency across the wide input range, the RAs incorporate dynamic biasing and dynamic voltage scaling through an auxiliary LDO. The RA-LDO also dynamically adjusts pluggable pass gates (PPGs), effectively extending the load current range up to 2 A. A prototype was fabricated in a 40-nm CMOS process, occupying an active area of 0.073 mm$^{2}$. The prototype achieved a voltage droop of 50mV and a settling time of 32ns in response to a load step of 1A/ns at an input voltage of 0.9V and an output voltage of 0.8V.