Research And Design Of A Capacitorless NMOS Low Dropout Regulator

With the continuous reduction of semiconductor process size and the rapid development of artificial intelligence technology,various portable devices have begun to integrate into people’s lives.Power management chips play a role in the conversion,distribution,detection and other power management of electrical energy in electronic equipment systems.Among many power management products,low drop-out regulators（LDOs）have become a low-cost solution for electronic devices by virtue of their stable output voltage,low noise,and the need for fewer peripheral devices.Compared with the traditional LDO,the off-chip capacitor-free LDO further saves cost and improves integration,which is of great research significance.This article firstly introduces the theoretical basis of traditional LDO,focuses on stability and transient characteristics,and compares it with the off-chip capacitor-free LDO.Based on this,the off-chip capacitor-free LDO designed in this paper is proposed,the system structure and working principle are described in detail,and the functional implementation of the main modules and simulation results are given.Finally,the simulation results and layout implementation of the overall circuit are given.The design uses NMOS as power transistors,using capacitor and a servo amplifier to provide DC operating points for the gate of the power transistor,reducing the noise impact of the internal charge pump.The dynamic output range of the error amplifier is increased by sampling the output current,and the transient response of the circuit is improved.The LDO also has excellent performance indicators such as low drop-out voltage,high accuracy and high power supply rejection ratio,which is very suitable for portable devices.Based on the HHGrace 0.35μm BCD process,and verified by Cadence Spectre simulation,the results show that the LDO has a dynamic output voltage range of 1.2V to 5V with a maximum load capacity of 400m A when the input voltage is 1.7V to 5.5V;the typical value of dropout voltage is 61m V;the linear adjustment rate is0.00368%;the maximum load adjustment rate for a load current in the range of 1m A to400m A is 0.002%,and a maximum load adjustment rate of 0.001%in the range of10m A～400m A;in the frequency band of 10Hz～100k Hz,the output noise voltage is59.4μV_RMS.