A current-limiter-based soft-start scheme for linear and low-dropout voltage regulators

A soft-start strategy for linear and low-dropout voltage regulators based on a successive current-limiting scheme during the startup phase is presented. The proposed current-limiting scheme incorporates a digitally-programmable mechanism for precisely controlling the current profile of the pass device during the startup transient. The proposed scheme is compact, as it requires no external components and has minimal transistor overhead, thereby minimizing the implementation area and cost of the overall regulator. The proposed soft-start circuit has been developed on a standard 0.35-μm CMOS technology as part of a USB-powered linear regulator for portable power applications.