A Fully On-Chip Digitally Assisted LDO Regulator With Improved Regulation and Transient Responses

This paper presents a fully on-chip mixed-mode low-dropout (LDO) regulator with improved regulation and transient responses. With the help of the digital regulation part, the supported maximum load current is significantly improved, while the chip area overhead is very small. A Miller compensation capacitor and a buffer stage are used to achieve stability and improve power MOS gate slew rate. The ultra-fast voltage buffer helps further improve the load transient recovery speed and reduce the chip area due to its wider voltage swing. A proof-of-concept LDO design is fabricated in a standard 0.18-mu m CMOS technology. The maximum load current is 150 mA, the output voltage is 1 V, and the dropout voltage is 0.2 V. The load regulation is 0.17 mV/mA, which is more than 480% improved over the traditional design without digital assistance.