A 2 x VDD-Enabled Output-Capacitor-Free Low-Dropout Regulator with Fast Transient Response for Low-Cost System-on-Chip

This paper presents a 2 x V-DD-enabled output-capacitor-free CMOS low-dropout (LDO) regulator with fast transient response for cost-effective system-on-chip (SoC) power management applications with elevated-V-DD supply. All the MOS transistors used in the proposed LDO regulator are low voltage (LV) MOSFETs, hence saving the high voltage devices fabrication cost required in a conventional design. Two LV power transistors are cascaded in the power train. A mid-rail regulator is used to generate 1 x V-DD voltage for the power transistors as well as the main error amplifier to guarantee safe operation. The mid-rail regulator employs stacking transistors to handle the high supply voltage. Moreover, Miller compensation with adaptive biasing is used to achieve good stability and fast transient response. A proof-of-concept design is fabricated in a standard 0.18-mu m CMOS process which achieves 3.3-3.6 V nominal input, 3.1 V nominal output and 100 mA loading capability with all the transistors being 1.8 V MOSFETs.