A Self-Triggered Digitally Assisted Hybrid LDO with 110 ns Settling Time in 65 nm CMOS

Abstract

This article presents a self-triggered digitally assisted hybrid low-dropout regulator (LDO). The proposed architecture uses an analog LDO for steady-state operation and a digital LDO to track large output current changes. The dual loop has a loop controller for coherent operation, and the digital loop is only triggered when there is a large load step. Therefore, the proposed LDO inherits some of the advantages of both parts. It achieves a high power supply rejection ratio (PSRR) from the analog part. The digital loop has a faster settling time and consumes less static power than the analog loop. In this design, the maximum load is 200 mA. For heavy load conditions, PSRR is -40 dB at 1 MHz. The quiescent current is 200 & mu;A. The undershoot/overshoot with the corresponding settling time measured under a load current step of 200 mA/10 ns are 82 mV/89 ns and 112 mV/110 ns, respectively. The proposed LDO achieves a competitive 4.48 ps figure of merit. In the TSMC 65 nm process, the active area is approximately 0.027 mm(2).