Analyze Power Supply Rejection Ratio of LDO Regulator Based on Accurate Small Signal Model

The power supply rejection ratio (PSRR) is a crucial specification for the low-dropout regulator (LDO). Many circuit topologies have been proposed to achieve high PSRR for the LDO. To simplify the design flow, most analog circuit designers estimate the PSRR performance based on the small signal model. However, the accuracy of the small signal model for PSRR has not been verified. In this paper, the accuracy of the general small signal model has been analyzed. A new small signal model for PSRR of LDO has been developed and verified. The simulation results shows that the accuracy has been improved significantly while the new model is applied comparing to the general model. The simulation results has been verified using a standard 0.35-µm CMOS process technology