Smooth Pole Tracking Technique by Power MOSFET Array in Low-Dropout Regulators

Abstract

This paper proposes an advanced Q-reduction technique of pole-splitting compensations for low dropout (LDO) regulator. The output pole is load dependent and may cause the scenario of complex poles when load current changes. LDO regulators may oscillate because high-Q incurs the less gain and phase margins. The reasons of causing complex poles depend on the design methodology. For the design of capacitor-free LDO regulator, high-Q issue happens when load current changes from heavy to light. Recent literature provides a method to alleviate the high-Q problem. However, large dropout voltage in case of suddenly large loads forces designers to include a small load capacitor as an indispensable component for supplying system-on-chip (SoC) systems. Different to the case of capacitor-free LDO regulators, high-Q issue happens when load current changes from light to heavy. According to our proposed power MOSFET array, the high-Q problem can be alleviated and prevent LDO regulators from oscillating when load changes. Experimental results promise the stability and show the improvement of load and line regulations.