This paper presents a capacitor-less CMOS low dropout regulator (LDO) with a push-pull class AB amplifier, and a fast transient controller to achieve a better transient response. The undershoot/overshoot voltage and the settling time are effectively reduced. Through the theoretical analysis of the circuit, cadence simulation with SMIC 0.18μm process and under the condition of the input voltage range 1.4~4 V shows the output voltage is 1.2 V, with the fast controller the total quiescent current is 8.2 μA, the undershoot /overshoot voltage is 97 mV/47 mV and the settling time is 0.3 μs as load current suddenly changes from 1 to 100 mA, or vice versa. Compared with this paper without fast transient controller, the undershoot voltage, the overshoot voltage and the settling time are enhanced by 30%, 64% and 80%, respectively.
Design of a Low-Noise, Fast Set-up and Low-Voltage Low-Dropout Regulator Featuring 230mA Load Current Range