A Capacitive Step-Down Converter Using a Linear Mode Pre-Regulator for Improved Load Regulation

A capacitive step-down converter in 0.25 mum CMOS using a linear mode pre-regulator is presented. The linear pre-regulator operates both in pulse frequency mode under low load conditions and in current mode under high output load. In pulse frequency mode the pre-regulator limits the charge current of the capacitor network improving the electromagnetic compatibility. Under high load conditions the converter operates in a current mode which means that the switched capacitors are clocked with a fixed duty cycle ratio and the regulation of the output voltage is performed by the pre-regulator