| With the rapid development of artificial intelligence and integrated circuit industry,a variety of smart home and portable electronic products have come into people's lives.They have not only changed people's way of life and entertainment,but also greatly improved people's quality of life.However,while electronic products bring benefits to people,people also put forward higher performance requirements for electronic products,As the most important part of electronic products,power management chip determines the performance of electronic products to a certain extent.At present,for the linear regulator which occupys the leading position in the market of power management chips,researchers are making efforts towards the development trend of low power consumption,on-chip compensation,fast response,high precision,digitization,high stability and so on.In this paper,a linear regulator with low dropout and high precision is designed.The circuit is mainly composed of error amplifier,source follower,feedback control loop,band gap reference,bias current source,over temperature protection circuit and other modules.In the circuit design,in order to obtain high output voltage accuracy,a reference voltage source with high power rejection ratio and low-temperature drift is designed.A two-stage amplifier is added to the reference circuit to reduce the nonlinear error,and a segmented temperature compensation is added to reduce the temperature drift.In addition,a folded structure with high gain and easy frequency compensation is used in the design of the error amplifier.In this way,the accuracy of output voltage can be improved by improving the accuracy of bandgap reference voltage and the gain of feedback loop;in order to get a smaller dropout voltage,the power tube uses P(PMOS)tube;In order to obtain high-precision bias current,an adjustable cascode current source is designed;in order to improve the loop stability of the system,the system circuit uses miller compensation and pole-zero tracking frequency compensation to carry out frequency compensation;in order to improve the power supply rejection ratio of the system,many parts of the circuit are optimized,such as using cascode structure,using the P-type current mirror as the load of amplifier in the circuit using the P-type transistor as power tube and so on;in order to improve the response speed of the system,a buffer stage is added in the traditional circuit structure;in order to prevent the temperature of circuit from being too high causing abnormal situations,the over temperature protection module is added in the circuit.This design is based on TSMC's 0.18?m process and uses Cadence spectre to simulate the circuit.The results show that when the input voltage is in the range of 2.7V-3.3V,the output voltage is 1.8V,the output current is in the range of 0-200 m A,and the dropout voltage is 600 m V.The circuit can keep stable under light,medium and heavy load,and has high power supply rejection,86 d B at low frequency.When the load current jumps from 1m A to 101 m A in 1 ?s or from 101 m A to 1m A in 1 ?s,the transient changes of output voltage are less than 40 m V,the system linear adjustment rate is 0.19 m V/V,and the load adjustment rate is 0.006 m V/m A.In summary,the performance of the circuit meets the design goals. |
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