A Low-dropout Regulator with Unconditional Stability and Low Quiescent Current

Abstract

An unconditionally stable low-dropout regulator (LDO) with ultra low quiescent current is presented. By using frequency compensation of dynamic miller on the LDO's structure, the proposed LDO's stability is independent of the load or off-chip capacitor. The LDO works at a low quiescent current of approximately 4 muA. Low quiescent current is due to a precision CMOS current reference, which operates in subthreshold region and generates 30 nA bias current. The current reference has max-to-min fluctuation of less than 2.5% over a temperature range of -40 degC to 150 degC. The proposed LDO has been implemented in a 0.5-mum CMOS technology. The experimental results revealed that the LDO provides a full load transient response of less than 50 mus setting time and less than 75 mV overshoots and undershoots. Moreover, the dropout voltage is 170 mV at 150 mA loading, and quiescent current is 4.17 muA when output current is 150 mA