Design And Implementation Of Low Voltage LDO With Stable Low Ripple Output In 2A Load Range

With the development of electronic products,the types of electronic products and the running speed of electronic products are also faster and faster.As an essential part of every equipment,power management IC is becoming more and more important for its stability and ripple output.Low Dropout Regulator(LDO)has higher load adjustment rate,higher linear adjustment rate and better performance.The characteristics of small ripple voltage output and better output noise have been widely used.However,in the actual application of product projects,some LDOs will appear self-excitation phenomenon,which is mainly due to LDO as a closed-loop system,its loop baud diagram affects its loop stability.Loop baud diagram changes under different loads,so under specific loads,there will be LDO closed-loop system instability.At the same time,if LDO closed-loop system is unstable.The bad road characteristics also directly affect the output ripple size.After confirming the relevant LDO specifications and the LDO with better parameters in the actual test part,it is found that almost all brands of LDO on the market can not meet the requirements of better loop stability and low ripple output in the wide load range,and thus can not meet the larger load variation of electronic products,stability and transmission.The ripple can not be guaranteed to the maximum extent.Therefore,this paper is dedicated to this problem,in-depth study of LDO,research and design a LDO with better loop stability and lower output ripple in the 2A load range.Firstly,this paper studies the classification,basic framework and basic principle of LDO,summarizes and analyses the current situation of LDO and related technologies,and puts forward the technologies to be achieved in this paper according to the stability criterion of closed-loop system in signal and system,the ripple of power supply and PSRR requirements of SOC and other consumer power modules.Parameter index standard.Secondly,in order to achieve this series of technical indicators,a special LDO under the branch of LDO is studied.CMOS LDO,which is also the mainstream low-voltage-difference linear power supply in the future,will change with the change of load due to the adjustment of junction capacitance,load capacitance and frequency response of error amplifier in the framework of traditional CMOS LDO principle,and then affect the closed-loop feedback system of LDO.Stability and output ripple,so this paper proposes a new CMOS LDO principle framework which can meet the design requirements of this paper,and makes a detailed description and analysis of the internal parts of this new principle framework structure diagram,clarifies the technical implementation scheme of the principle framework structure,and ensures that the technology has a corresponding supporting role for the follow-up technical research of this paper.Secondly,the main components of the new CMOS LDO principle framework,current detection,are studied,analyzed and simulated in detail.Because it is difficult for LDO to achieve high stability and low ripple output in wide load range,the quality of current detection circuit directly determines what error amplifier LDO uses under different loads,and then determines the stability of the whole LDO and the size of output ripple.Thirdly,the main component of the new principle framework,error amplifier,is studied,analyzed and simulated in detail.Because the design of error amplifier has better characteristics in wide load range is very difficult and the cost is quite high,so this paper proposes the circuit structure of double error amplifier,which can switch different error amplifiers under different loads,so as to avoid the shortcomings of different error amplifiers under different load conditions and highlight their respective advantages.Then,for several other important modules in the new CMOS LDO principle framework: the regulator,the switch of the light-load and heavy-load error amplifier and the single-ended signal to differential signal circuit,relevant research,analysis and corresponding circuit simulation tests are carried out to ensure the feasibility of the whole technical scheme and the smooth construction of the subsequent system debugging test simulation model.Finally,this paper builds and combines all parts together,uses PSPICE simulation software,combines the simulation parameter conditions of all modules,tests the loop curve,load jump ripple and PSRR of the whole system,and through continuous debugging,testing and simulation,achieves the technical parameters at the beginning of the paper design,and meets the requirements of good loop characteristics and low transmission in 2A load range.The purpose of this paper is to study and design a LDO with good ripple stability in the 2A load range.