A Wide-Load-Range and High-Slew Capacitor-Less NMOS LDO With Adaptive-Gain Nested Miller Compensation and Pre-Emphasis Inverse Biasing
Hyunjun Park, Woojoong Jung, Minsu Kim, Hyung‐Min Lee
Abstract
This article proposes an output capacitor-less NMOS low-dropout regulator (LDO) using wide-range adaptive-gain nested Miller compensation (WAG-NMC) and pre-emphasis inverse (PI) biasing. Due to WAG-NMC, the LDO can provide a wide range of load current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm {LOAD}}$ </tex-math></inline-formula>) from 0.1 to 300 mA while maintaining sufficiently high phase margin (PM) above 60° at all <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm {LOAD}}$ </tex-math></inline-formula> conditions. WAG-NMC also extends a loop bandwidth (BW) up to 17.5 MHz with using only small compensation capacitors (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{\text {C}}$ </tex-math></inline-formula>) of 6.3 pF in total. Moreover, PI biasing enhances a slew rate (SR) at the gate of the NMOS power transistor by injecting an adaptive PI current into a supersource follower (SSF), which further improves transient response. The proposed LDO fabricated in a 180-nm CMOS process was fully integrated with an on-chip load capacitor (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{\text {L}}$ </tex-math></inline-formula>) of 100 pF. The LDO ensures small undershoot and overshoot of 48 and 59 mV, respectively, against large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta I_{\mathrm {LOAD}}$ </tex-math></inline-formula> of 299 mA due to wide-BW and high SR. The proposed LDO also achieves a best figure of merit (FoM) of 1.72 ps among the state of the arts.