Stability And Frequency Compensation Technology Of CMOS Low Dropout Regulator

The thesis focuses on the study of the stability characteristics and frequency compensation of LDO linear voltage regulator. The Various kinds of factors of unstability which are generated in LDO linear voltage regulator have been analyzed. Five kinds of frequency compensation techniques are presented. And then, advantages and features of these five frequency compensation technologies have been discussed. At last, a novel and practical frequency compensation method is discussed in detail in this paper to solve the stability of LDO. Compared with conventional methods, the proposed scheme not only succeeds in pole-splitting, but also generates a zero internally without any extra ESR resistors, which indeed helps increase system's phase margin and result in stability. This scheme is an area-saving one and it is capable of maintaining system stability. The whole circuit is simulated with BSIM3V3 Spice model in Hspice based on CSMC 0.6um. Simulation results indicate an improved phase margin and transient response in full load range.