A 200mA-Load 0.62fs-FOM Active-Capacitor-Assisted Dual-loop Output Capacitorless Low-Dropout Regulator in Standard 65nm CMOS.

This paper presents a new active-capacitor-assisted dual-loop output-capacitorless low-dropout regulator (OCLDO). As opposed to the conventional PMOS-based OCLDOs where the current load range is limited due to significant output variations under large load step changes, a dual-loop control scheme is proposed to improve the slew rates at transient-critical nodes and the regulation accuracy. To further speed up the loop response, a single-point-detection (SPD) active capacitor located at the output detects both positive and negative output variation together and reduces undershoot/overshoot and settling time without using any passive output capacitor. Implemented in a standard 65nm CMOS process, the proposed OCLDO delivers a maximum load current of 200mA. It only uses a small compensation capacitor of 0.86pF and achieves fast settling time of 110ns. It also has small undershoot / overshoot voltages of ≤ 160mV under load step changes of 200mA/100ns. Compared with previous designs, this work presents a fully on-chip PMOS OCLDO that provides the best transient FOM of 0.62fs.