A 2μA Quiescent Current Output-Capacitorless LDO with Adaptive Power Transistors for Low Power Management in Energy Harvesting

This paper presents a low quiescent current outputcapacitorless low-dropout (LDO) regulator implemented in 65nm CMOS technology dedicated to the power management in Energy Harvesting Unit (EHU) applications. Most of the blocks in the proposed circuit operate in the subthreshold region in order to provide their specific outputs while consuming less current. To further reduce current consumption, a subthreshold voltage reference which can also be used to bias the error amplifier while providing a voltage reference of 500.2 mV with a TC of 55ppm/°C and a power consumption of 433.2 nW is utilized. The proposed LDO regulator uses a current-efficient adaptively biased regulation using two power transistors. The adaptive biasing circuit senses the load current and adjusts the bias point of the amplifier correspondingly. The results from the simulation demonstrate that the low dropout regulator can achieve a remarkably low quiescent current of 1.98859uA and a power consumption of 2.349134 uW under no load conditions. Additionally, the LDO regulator has a PSRR of −50.3228 dB, a good stability margin of 72.66°, and a maximum settling time of 3.437 us all under different load conditions. Moreover, the regulator can successfully maintain a regulated output voltage of 1V from a supply voltage of 1.2V, with a dropout voltage of 200 mV leading to an overall efficiency of 83.33%. Furthermore, the overall chip layout area is 0.0739 mm².