Double-Loop Compensation Technique for LDO with a Wide Load Range

Abstract

With the increasing development of automotive electronics, the requirement of low dropout regulator (LDO) with a wide range of load currents and load capacitances becomes more and more important. In this paper, a double-loop compensation (DLC) technique is presented to over the limitation of conventional Miller compensation. For clear analysis, pole motion method is adopted for the first time, which combines the effect of inner and outer loops under wide load in detail. Besides, the phase margin that restricts the stability of control loop with changes in two-dimensional variables (load capacitance and load current) is explored. Different from conventional methods, the proposed analysis method can more effectively obtain the frequency compensation requirements of wide load capacitances and load currents. Finally, DLC technique is verified in LDO structures.