Research And Design Of Transient Enhanced Low Dropout Regulator

Low Dropout Regulator(LDO)has these performances that include low noise,low power consumption and simple circuit structure,and it has become an important member of power management chips.With the development of System on Chip(So C),LDO without off-chip capacitor are one of the important trends of power management chips.Based on those,this thesis researches and designs a kind of transient enhanced LDO without off-chip capacitor.The main contents including:Firstly,based on the analysis of the traditional bandgap voltage reference(BGR),a curvature-compensation BGR is designed.And,a piecewise curvature-compensation BGR is given in this thesis.Simulation results show that the designed piecewise curvature-compensation BGR achieves the reference voltage with the temperature coefficient of 0.4ppm/°C and it has the power supply rejection ratio of-93.7d B at low frequency.Secondly,the error amplifier of LDO is analyzed in thesis.According to the design requirement,the structure of two-stage error amplifier is identified.Based on these analyses of traditional frequency-compensation technique for three-stage amplifier,a kind of LDO is given by adopting the technique of pole-zero tracking frequency compensation and miller compensation.Simulation results show that the designed LDO achieves the loop gain of 101 d B and the loop phase margin of 89° with the load resistance of 16Ω.When the load resistance is 16kΩ,the designed LDO achieves the loop gain of 124 d B and the loop phase margin of 55°.Finally,based on the analysis of transient response of LDO,a transient enhancement circuit is given by adopting the technique of comparator.The over-temperature protection circuit and over-current protection circuit are designed for LDO,and the system of transient enhanced LDO without off-chip capacitor is given.Simulation results show that the designed system of transient enhanced LDO without off-chip capacitor achieves these performances including output voltage of 1.6V,the maximum load current of 100 m A,the dropout voltage of about 200 mV,the temperature coefficient of 15.1ppm/°C,line regulation of 1.89 mV/V and load regulation of 0.556 mV/A,and the power rejection ratio reaches-72.6d B at low frequencies.When the load current changes between light load and heavy load,the system of transient enhanced LDO without off-chip capacitor has these performances including the response time of 3.48μs and 11.51μs,the under-shoot voltage of 396 mV and the over-shoot voltage of 200 mV.