Research And Design Of On-chip Low Dropout Linear Regulator

Low Dropout Linear?LDO?Regulator is widely used in power management chips for various portable mobile devices due to its advantages such as low noise,high power supply rejection,stable output and excellent load regulation.With the development of system on a chip?SoC?,on-chip LDO regulator becomes a hot spot in the design of power management system.Based on those,a kind of on-chip LDO regulator for SoC was designed in SMIC 0.18?m CMOS process in this thesis.The main work includes the following:Firstly,on the basis of introducing the working principle and temperature characteristics of the traditional Bandgap Reference?BGR?circuit,several typical temperature compensation techniques were discussed.Based on those,a high-order temperature-compensated bandgap reference voltage source was designed by adding a current proportional temperature T^1.5 to the traditional BGR circuit and adopting picewise temperature compensation technology.Simulation results showed that the designed BGR achieved the temperature coefficient of 3.71ppm/°C and the power supply rejection ratio of-136dB at low frequency.Secondly,on the basis of analyzing the frequency compensation of the on-chip LDO and the classical frequency compensation techniques of three-stage operational amplifier,a nested-miller-active-feedback-compensation?NMAFC?three-stage amplifier was designed by adopting nested miller compensation?NMC?and active feedback frequency compensation?AFFC?technology,which can drive large capacitor loads.Simulation results showed that the deisnged three-stage amplifier achieved the DC gain of 112dB,the phase margin of 68°and the unity gain bandwidth of 4.92MHz.Finally,the auxiliary circuits of the on-chip LDO regulator system,which included short-circuit protection,overcurrent protection,over-temperature protection and transient enhancement,were analysed and designed.Based on the designed NMAFC three-stage operational amplifier,an on-chip LDO regulator for SoC was designed in SMIC 0.18?m CMOS process.Simulation results showed that the designed on-chip LDO regulator achieved the dropout voltage of 195mA,the temperature coefficient of3.76 ppm/°C,the power supply rejection ratio of-90.1dB at low frequencies,the load regulation of 0.00034mV/mA and the linear regulation of 0.193mV/V.