Design Of Low-Dropout Regulator With Self-detecting Function

With the rapid development of integrated circuit industry,SOC is developing towards low power consumption,small size and high performance,and the performance requirements of power management circuit are constantly improving.LDO is widely used in various power management circuits because of its simple circuit and low cost.As LDO circuit can only be used when the working voltage is reduced.In the application of wide range input voltage,the chip often uses the boost circuit to supply power for LDO.As the circuit devices have the maximum withstand voltage,it is of great significance to study and design the protection of LDO circuit by limiting the output voltage of boost circuit by detecting circuit.Combined with the research of power management circuit,the thesis designs a LDO circuit with self detection function.According to the requirements of power input range,the thesis designs the architecture of charge pump and detection circuit as LDO power supply.Firstly,the thesis introduces the design idea of capacitor-less LDO in detail.By comparing the voltage drop and working current of various adjustment transistors,PMOS is finally selected;the nested Miller compensation method is adopted,Miller resistance and current buffer stage are added to ensure the loop stability of LDO,and feedforward stage is adopted to improve the transient response of LDO.Then,the cross coupled charge pump circuit is designed to increase the input voltage of the power supply,and the substrate potential of the output switch is dynamically biased to reduce the leakage current;According to the demand of the output load current,the size of the capacitor and the size of the switch transistor are determined,and the multi-stage inverter structure is designed to drive the charging capacitor.Finally,through the analysis of the maximum withstand voltage of the circuit device,the detection circuit structure is determined to limit the output voltage of the charge pump,so that the design does not need to use high-voltage transistor.The circuit is not limited by the process,and has a wider range of applications.This design adopts 0.18 μm BCD process,using Cadence software.The input voltage range is 2V～5.5V,the output voltage is 3.3V and the load current range is 10μA～ 30 m A LDO circuit with self detection function.The simulation results show that the maximum load current driving condition can be achieved in the overall voltage input range.Within the overall load current range,the LDO phase margin is above 60°,which meets the stability condition.When the load current changes transiently,the maximum overshoot voltage error of the output voltage is less than 5%,which meets the design requirements.