FRACTIONAL CHARGE PUMP FOR STEP-DOWN DC-DC CONVERTER

摘要

A charge pump provides a multiplication factor of 2/3 by using a three-phase mode of operation. In a first mode, first and second capacitors are charged from an input voltage while a third capacitor drives the output voltage based on stored charge in the third capacitor. In a second mode, the output terminal is connected to the common node of the first and second capacitors. In a third mode, the voltage potential across the second capacitor is subtracted from the sum of the input voltage and the voltage potential across the first capacitor to generate the output voltage. Operated in this manner, the first, second, and third capacitors will provide the desired 2/3x voltage multiplication. This relatively low multiplication factor can be beneficial in applications requiring 2.5V and 1.8V supplies for integrated circuits, particularly where the input voltage is provided by a lithium battery.