A Fast-Transient Response Digital Low-Dropout Regulator With Dual-Modes Tuning Technique

A fast transient response digital low dropout (LDO) regulator with a low quiescent current is proposed for power management applications in a self-powered wireless sensor system. The digital LDO incorporates both bisection method (BM) and steady-state tuning techniques to enhance the current efficiency and transient response speed. In steady-state period, the digital LDO works at steady-state mode and only one PMOS is switched at each clock edge for high accuracy and current efficiency. Once the variation of output voltage exceeds the detection boundaries, the BM mode is triggered and the required array conductance can be found in a short response time. The proposed digital LDO is fabricated using 65nm CMOS process. The measurement results show that with the load current switching between 0.1 mA and 4.5 mA, the proposed digital LDO shows a transient response time of 5.9 mu s with a maximum undershoot voltage of 118 mV at a regulated output voltage of 0.55V. The current efficiency is 99.7% and the figure of merit is 62.2 ps.