A 270-mA Self-Calibrating-Clocked Output-Capacitor-Free LDO With 0.15-1.15V Output Range and 0.183-fs FoM

Youngmin Park, Dongsuk Jeon

Abstract: This article proposes a fully integrated output-capacitor-free low-dropout regulator (LDO) for mobile applications. To overcome the limited output voltage range of typical analog LDOs, our design uses a rail-to-rail voltage-difference-to-time-converter (VDTC) and a charge pump (CP) to achieve a wide output range. Using a self-calibrating clock generator (SCCG) removes the need for an external clock source and adaptively tunes the clock frequency, enabling fast transient responses while minimizing quiescent current. A tunable undershoot compensator (TUC) mitigates voltage droop by detecting the drop in the output voltage due to a sharp increase in load current and compensating the output voltage immediately. The proposed LDO is fabricated in a 65-nm low power (LP) CMOS process and demonstrates a maximum load current capacity of 270 mA. The input and output voltage ranges of the LDO are 0.5–1.2 and 0.15–1.15 V, respectively, with 12.7- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> quiescent current and 99.99% peak current efficiency. The measured undershoot and settling time are 150 mV and 100 ns at a slew rate of 200 mA/3 ns, respectively, achieving a figure of merit (FoM) of 0.183 fs.