Research And Design Of Low Dropout Linear Regulator With Fast Response

With the rapid development of portable electronic devices,System on Chip(SoC)has become ubiquitous.The importance of power management chips is self-evident.Low Dropout Regulator(LDO),as one of the power management chips,is widely used in SoC because of its low cost,simple structure,low power consumption and low noise.In traditional LDOs,external capacitors not only play a role of frequency compensation devices,but also act as charge storage and discharge devices to reduce the impulse value of output voltage.However,the use of external capacitors will make the integration of SoC worse,which makes the development of capacitor-less LDO become an inevitable trend.When LDO is used as a power supply for digital-analog hybrid circuit,it is difficult to maintain the stability of LDO due to constant changes in load,what's worse,the output voltage of LDO may turn into an impulse voltagae that may be as low as ground potential.So it is necessary to design a transient enhancement circuit to optimize capacitor-less LDOs to provide a fast and low overshoot power supply voltage for circuit module.For high-precision systems,the accuracy of LDO is particularly important.In LDO circuits,the reference voltage has the greatest impact on the accuracy performance.In this paper,a current-mode voltage reference source with curvature compensation is proposed to improve the accuracy of LDO.In the voltage reference source,the temperature coefficient of the voltage reference is lowered by using CTAT current compensation technique and high-low temperature piecewise compensation technique.Chopper stabilization technique and second-order low-pass filter are used to reduce the offset voltage and the ripple effect caused by chopping.So that the accuracy of the reference voltage is improved and the overall performance of LDO is improved.In order to ensure the stability of the system and enhance the transient response,in the overall circuit design,the feed-forward stage circuit is used to enhance the gate swing rate of the regulator to speed up the transient response of the output terminal.Substrate modulation technology is used to speed up the transient response of the output terminal,at the same time,a left half-plane zero is introduced to compensate the frequency in the loop to maintain the stability of the whole circuit.The integrated circuit design is based on Dongbu 0.18?m CMOS process.The test results of the reference voltage source show that the temperature coefficient of the reference voltage is 4.85ppm/°C when the temperature range is-40°C~150°C at 5V supply voltage.The overall layout area of LDO is 0.13mm~2.The simulation results show that the temperature coefficient of the output voltage is 0.827ppm/°C over the temperature range of-40°C~150°C at 5V supply voltage;When the input voltage rangs from 3.5V to 5.5V,the output voltage is 3.3V;the maximum load current is 50mA;the differential voltage is less than 200mV;Under 5V supply voltage,the load regulation is0.053%/A,the linear regulation is 0.014%/V,the power supply rejection ratio is-63.5dB at full load,and the phase margin is above 80deg at no load and full load.The static current of the whole LDO is less than 200?A at all corner;when the load current jumps between 1 mA and 50 mA in 1?s,the maximum undershoot and overshoot of the output voltage are 49.3mV and 18mV,respectively.After using the substrate modulation technology,the simulation results of transient response show that the undershoot voltage of output terminal is reduced by about 75%,and the stabilization time is reduced to by 50%.