An external capacitor-less low drop-out regulator with superior PSR and fast transient response

In this paper, an external capacitor-less low drop-out (LDO) voltage regulator with superior power supply rejection (PSR) and small transient ripple is described. The proposed LDO has the advantages of wide-band PSR and fast transient response while consuming only 18μA of quiescent current. Simulation results show that the LDO designed in a mainstream 0.18μm CMOS technology presents a PSR better than -55dB up to 1MHz when loaded by a 100pF capacitor. The peak-to-peak undershoots and overshoots are less than 75mV when load current pulses from 0 to 50mA with 1μs rise/fall times. Load regulation is around 30mV/mA and output voltage deflection is under 75mV when sweeping the load current in the range 0-50mA.