A 1.39-V input fast-transient-response digital LDO composed of low-voltage MOS transistors in 40-nm CMOS process

A fast transient-response digital low-dropout (LDO) voltage regulator comprising only low-voltage MOS transistors was developed. The input voltage can be higher than the withstand voltage of the low-voltage MOS transistors by the proposed withstand-voltage relaxation scheme. The switching frequency of 1 GHz can be achieved using small-dimension low-voltage power-MOS transistors. The LDO occupies only 0.057 mm² area using 40-nm CMOS technology, and covers a wide range of load currents from 400 μA to 250 mA. The response time is only 0.07 μs.