Stability Analysis and Design Procedure of Multiloop Linear LDO Regulators via State Matrix Decomposition

This paper presents the application of the state space approach to analyze stability and robustness of multiloop linear low dropout (LDO) regulators. Because of the increasing complexity of the LDO architecture, the stability study consisting of an open-loop ac analysis is more and more difficult to apply. In this paper, we demonstrate how a state matrix decomposition of a system allows the stability analysis in closed loop to be performed where the open-loop ac analysis failed. Based on this technique, a methodology of design, a time response criterion, and a Monte Carlo analysis are proposed. The efficiency of this approach is illustrated comparing the classical open-loop ac study with the state matrix decomposition analysis of a complex innovative architecture LDO. The results are verified experimentally.