Transfer Function Analysis of the Power Supply Rejection Ratio of Capacitor-Less LDOs

This paper presents a rigorous transfer function analysis of the power supply rejection ratio (PSRR) of typical capacitor-less low-dropout (LDO) regulators. An efficient and accurate model is proposed to relieve the complication. The transfer functions, together with the poles and zeros, are obtained regarding a typical capacitor-less LDO topology as an example. The numerical results are plotted and compared to circuit simulation results using a commercial 65-nm technology for verification, and using the proposed model the mechanisms of different PSRR enhancement techniques are discussed. The proposed model and derived transfer functions match well with the simulation and measurement results in prior works.