A Compact Ramp-Based Soft-Start Circuit for Voltage Regulators

A fully integrated soft-start circuit for voltage regulators is presented in this brief. A soft-start strategy based on a linearly ramped-up reference is adopted to prevent massive in-rush currents through the power device during the start-up phase of the regulator. The strategy is realized by a compact on-chip circuit, which 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 implemented in a 0.35-mum high-voltage complementary metal-oxide-semiconductor technology as part of a linear regulator controller for automotive applications. The proposed soft-start circuit occupies 0.026 mm² on silicon, which corresponds to about one fifteenth of the total area of the linear regulator controller.