A 0.6-V High-Speed Digitally Controlled Low-Dropout Regulator with 99.8% Current Efficiency at 50-mA Load

A digital fast transient response low-dropout regulator which can work in both coarse and fine modes is presented. If the difference between reference voltage and output voltage is high, both coarse and fine circuits work simultaneously to provide higher speed for following the reference voltage, and when the difference between reference voltage and output is in the defined range, only the fine part of the proposed circuit is activated with lower operating frequency to both increase the output voltage accuracy and reduce the circuit power consumption. Designed in a standard 0.18-μm CMOS technology, the circuit occupies 195×255μm
²
of silicon area. Post-layout simulation results show that operating with 500MHz input clock signal, the maximum regulator delay is 250ns and the voltage ripple is less than 20mV in steady state condition with load and line regulation of 0.13mV/mA and 8.1mV/V, respectively. Furthermore, it reaches the current efficiency of 99.8% at a load current of 50mA. Operated with 0.78V supply voltage, the quiescent current is 90μA, with achieving of 0.072ps figure of merit.