Adaptive driving for optimum LDO transient performance

Abstract

This paper presents a driver used in low-dropout linear voltage regulators (LDOs) in order to optimize the transient performance in terms of undershoot and overshoot. The driver structure includes two different type buffers: first one is a pMOS source follower and the second one is a nMOS source follower. They are cascade connected and in function of regulator's output current, the second one is bypassed. At low output currents, the driver works as a simple pMOS buffer assuring an optimum undershoot performance in case a positive load jump occurs. At high output currents, the driver works as a two stage buffer (PMOS buffer followed by nMOS buffer) and assures an optimum overshoot performance in case a negative load step occurs.