A transient-enhanced output-capacitorless LDO based on push-pull with source degeneration and capacitor feedback

Abstract

A push-pull buffer with source degeneration output structure is proposed as an intermediate stage for an output capacitorless low-dropout regulator (OCL-LDO) in this paper. The proposed push-pull buffer with source degeneration output structure can increase the current for charging and discharging the gate capacitance of the power transistor during the transient instant, effectively improving the transient voltage slew rate at the gate of the power transistor, thereby enhancing the transient response of LDO. Additionally, a transient overshoot reduction (TOR) circuit is employed to suppress the overshoot phenomenon during transient response. The proposed LDO is implemented using 0.18 μm CMOS technology. Simulation results indicate that the LDO can operate from a supply voltage of 1.2-1.8 V with a minimum dropout voltage of 0.2 V at a maximum 50 mA load and quiescent current of 22 μA. With a load current step from 200 μA to 50 mA within 10 ns, the maximum value of the voltage spike is 160 mV and the maximum recovery time of the LDO is 0.88 μs.