Research And Design Of A High Current High Power Supply Rejection Ratio LDO Regulator

Linear regulators are crucial analog blocks that shield a system from fluctuations in supply rails.LDO is widely used in circuit systems with high requirements for power supply noise limitations due to its simple structure,low dropout voltage,low noise,high ripple rejection,fast response and increasing efficiency.At present,the technical difficulties and research directions of LDO are mainly focused on high stability,high PSR,fast response,fully integrated,low power consumption and so on.This thesis focuses on the study of LDO voltage regulators based on bipolar process,and proposes a negative low dropout linear regulator with large output current and high power supply rejection ratio.Powered by a negative supply rail,it is convenient to use the common-emitter NPN as the power switch transistor,taking advantage of its larger current gain to reduce the quiescent current while also ensuring a lower dropout voltage of 300 mV and 1.5A output current.Creatively merge the error amplifier and the band-gap reference together,which saves the chip area,reduces noise and quiescent current.In order to lower the output capacitance restrictions,a Miller compensation structure with a current buffer is adopted,making the regulator remain stable with a minimum 10 uF output caoacitor,and a small ceramic capacitor can be used without the necessary addition of ESR,which also helps boost PSR performance at high frequency.In addition,the LDO also has an overcurrent protection circuit with an precision current limit with foldback and a thermal protection circuit with hysteresis.Through analyzing a simple impedance-ladder model for PSR,the key factors influencing the PSR and measures to improve the PSR are given.Finally,through the Cadence simulation software,the important parameters and performance indicators of the proposed LDO are simulated and optimized.Simulation results show that the parameters have met all the design requirements with an excellent regulation performance,especially PSR at 10 MHz high frequency is still greater than 25 dB.