Dual active capacitive feedbacks for output capacitor-less low-dropout regulator

Abstract

An output capacitor-less low-dropout (OCL-LDO) voltage regulator with dual active feedback paths is presented in this paper. The dual active feedbacks provide frequency compensation and spike voltage suppression. Two feedback loops are formed by capacitors C-c and C-a, respectively. The capacitor C-a path detects output voltage to suppress undershoot and overshoot during load transient. The frequency compensation is achieved by capacitor C-c, which helps the LDO regulator not only improve stability, but also enhance transient response without large current consumption. The total utilized capacitance values are only 1.5 pF. The proposed OCL-LDO was fabricated in 0.18 mu m CMOS technology with supply voltage of 1.8 V. The LDO consumes 21 mu A of quiescent current and the chip area is 0.47 mm x 0.49 mm. The measured output voltage difference is 90 mV when the load current is increased from 50 mu A to 100 mA with C-L= 100 pF and recovery time less than 1 mu s. The power supply rejection is - 51.7 dB at 1 kHz.