A Fast Transient Low-Dropout Regulator with High-Power Supply Rejection

Abstract

With the continuous popularization of portable electronic products in electronic information, aerospace, biomedicine and other fields, low-dropout regulator (LDO) has become an important part of modern power management chips. Compared with other power management modules, it has the advantages of low power consumption, high power supply rejection, and strong anti-noise capability. However, the LDO power tube has a large width-to-length ratio, so when the load changes transiently, the gate of the power tube cannot respond in time, resulting in an overshoot and undershoot of the output voltage and a long recovery time. In this paper, the LDO transient enhancement circuit is designed. When the load changes transiently, the power tube gate capacitor is quickly charged and discharged, which overcomes the overshoot voltage and undershoot voltage. While improving the transient response of traditional LDO, the structure ensures the power supply rejection (PSR) and other performance of the circuit. According to the results, with an input of 2.5 V, the output voltage is regulated to 1.2 V, and PSR is -80 dB. When the load changes by 20 mA in 1 μs, it is stable within 1.2 μs while the undershoot voltage is controlled at 51 mV and the overshoot voltage is controlled at 65 mV.