An electron mobility independent pulse skipping regulator for a programmable CMOS charge pump

A charge pump with a soft start-up control system and programmable regulated output is proposed in this paper for battery powered applications. The existing technique of a pulse skipping frequency regulator (PSFR) has been used to obtain a good efficiency over a wide range of loads. However, a new architecture for the PSFR with some improvements like a beta-independent behaviour and a programmable threshold voltage has been designed. The power-up control strategy that has been developed combines a linear and a switched charging sequence in order to avoid great current spikes at the start-up instant. Hence, the battery performance and the transistors of the charge pump are kept without any damage that could be produced by such initial current spikes. The result is a fully CMOS charge pump capable of generating a programmable and regulated output voltage from 3.3V up to 5.5V and deliver a maximum power of 100mW. This circuit has been implemented in 0.7 μ I²T technology from AMI semiconductor.