A Low-Dropout Voltage Regulator with a Fractional-Order Control

Abstract

This paper presents a 5 V / 50 mA low-dropout voltage regulator (LDO). The LDO uses a fractional-order control for its regulation loop to achieve a high DC gain (for a tight DC regulation) while avoiding (for a good stability) a high gain at high frequency. No compensation zeros are needed. The unity gain frequency of the regulation loop also changes adaptively with the output current to maintain it below the frequency of non-dominant poles. The LDO is stable with any external capacitance larger than 50 nF, and is expected to operate in a harsh automotive environment, with junction temperature ranging from -40°C to 170°C and with supply voltage from 7 V to 36 V. The operation of the LDO has been verified by realizing it in the 350 nm I3T50 ON Semiconductor technology.