slyt187Power Management Texas Instruments Incorporated Understanding the stable range of equivalent series resistance of an LDO regulator By Bang S. Lee Application Specialist, Power Management This application note explores the stable range of equivalent series resistance (ESR) values for LDO regulators. An ac model of an LDO regulator is presented to discuss the LDO frequency response. Both stable and unstable ESR ranges are examined. Figure 1. An ac model of a linear regulator Series Pass Element G + vgsg p Rds D Zo + R2 ga R1 VREF ……