A 0.7 V input output-capacitor-free digitally controlled low-dropout regulator with high current efficiency in 0.35 μm CMOS technology

This paper presents a discussion on an ultralow supply voltage low-dropout regulator (LDO) using a digitally controlled technique. Based on a 0.35 μm standard CMOS process with VTN≈0.5 V and |VTP|≈0.7 V, measurement results showed that the proposed digitally controlled LDO can operate from 0.7 V to 0.9 V with a dropout voltage of 200 mV. At a supply voltage of 0.9 V, the proposed LDO is capable of providing a regulated output of 0.7 V and delivering a maximal load current of 50 mA at 99.9% current efficiency. With the proposed LDO operated at 1 MHz clock, the measured quiescent current is only 4.7 μA. No external output capacitor is required to stabilize the control loop. For a supply voltage of 0.9 V, the proposed digital LDO features a tunable transient time with a maximal operating frequency up to approximately 14 MHz. The proposed LDO can also operate at supply voltages of 0.7 V in a 0.35 μm standard CMOS process. For an input voltage of 0.7 V and an output voltage of 0.5 V, the proposed LDO can deliver a maximal load current of 5 mA, which meets the specification of recently published 0.5 V applications. With these advantages, the proposed digitally controlled LDO is suitable for low-voltage and low-power applications.