Step-down converter with switched capacitors at high frequency

The characteristics of two hybrid step-down charge-pump voltage regulators (2.5, 1.25V) are presented. The regulators feature a current multiplication factor 4 and two capacitor banks structure which allows to work easily in the megahertz region and with currents up to 1.5A. Attention has been dedicated to the study of the power efficiency as a function of the frequency, in particular to the charge transfer factor leading to the voltage efficiency which has been fully described in an analytic way. This has allowed to evaluate possible improvements of the present prototypes.