A 22-nA Quiescent Current, 50-mA Output-Capacitor-Less Low-Dropout Regulator With Multiple-Feedback Loop for IoT Devices

This brief presents an ultra-low power, output-capacitor-less low-dropout regulator (OCL-LDO) with a multiple-feedback loop (MFL) for Internet-of-Things (IoT) devices. The proposed LDO consists of five feedback loops that offer excellent steady-state and transient performance. A tri-loop flipped-voltage-follower (FVF) stage enhances both line and load regulation. The slew-rate enhancement loop based on source cross-coupled error amplifier (SXCEA) provides a fast transient response. Moreover, the proposed LDO utilizes a dynamic feedback loop that significantly improves the undershoot recovery time during the full load step current. The design was fabricated in a 65-nm low-power CMOS process and occupies an area of 0.025 mm2. The LDO can deliver a maximum of 50 mA load current at a 1 V output voltage and consume only 22 nA measured quiescent current. The measurement results show that the proposed LDO achieves a load regulation of 0.004 mV/mA and a low-frequency power supply rejection (PSR) at full load of -63.5 dB. For a load current step from 200 nA to 50 mA with a 10 ns edge time, the measured voltage undershoot is 574 mV and settles within 200 ns. We achieve a figure-of-merit of 0.5 fs.