Design Of A High Stability And Fast Transient Response LDO

With the rapid development of portable intelligent equipment and automotive electronic products,the requirement of power supply and power management chip is getting higher and higher.Low-DropOut linear regulators(LDO)is one of the important components of power management chip,it has the characteristics of low noise,no output ripple,simple structure and low cost,which makes it very suitable for the integration of on-chip system and the high performance analog circuit.The traditional LDOs often need an external micro-level output capacitor.The output capacitor can be used to frequency compensation,reduce the output noise and accelerate transient response.The output capacitor and its equivalent series resistance(ESR)form a left half plane zero to counteract the influence of the secondary pole on the stability of the circuit.In this way,the value of the output capacitor and the ESR are critical to the stability of the entire circuit,which limits the range of ESR.In addition,the value of RSR is often easily affected by the external environment,which may lead to a large change for the value of ESR,and the stability of the circuit is reduced.The main goal of this paper is to design a LDO with high stability and fast transient response.The stability of this circuit can be guaranteed when the impedance of its ESR changes greatly.Firstly,the paper introduces the basic principle and parameters of LDO,then,the frequency compensation method of this paper is derived from the traditional Miller effect,afterwards the transient response process is discussed and the method to improve the transient response is given.Finally,complete the design of the circuit,including bias module,reference and error amplification module,overcurrent protection module,overheat protection module,driving module and startup module.The circuit design is based on a 32 V bipolar manufacture process.The simulation results show that the fixed output voltage is-1.21V?-2.5V?-3V ?-3.3V ?-5V ?-12Vand-15 V.The output current range is 1mA-1.5A.The quiescent current is 1.1mA.The dropout voltage is 310 mV.The linear regulation rate is 0.87 mV / A,the load regulation is 3.6mV / A,and PSR is 80 dB at 1KHz.When the capacitance of the output capacitor changes from 1uF to 10 u F,and the impedance of the ESR changes from 1m? ~ 1?,the circuit can guarantee the stability.When the capacitance of the output capacitor is 10 uF and the impedance of the ESR is 10m?,and the output current flips from 50 mA to 1.5A,the peak of the output voltage is less than 3.4%,the output voltage can be stable in 20 us.