Improved charge pump circuits for standard CMOS technologies

Reliability problems such as gate-oxide voltage overstress have become a concern for CMOS circuits as the gate-oxide thickness is scaled down. Gate-oxide overstress is particularly worse for charge pump circuits because they usually operate in high voltage levels. Devising charge pump circuits that avoid such problem is far simpler for CMOS triple well technologies than for standard technologies, nevertheless fabrication costs are higher. Two approaches are usually applied to eliminate gate-oxide overstress in charge pumps designed for standard CMOS technologies, the first is multiple phase control, and the second is dual phase control with doubled voltage swing. The latter has been shown to produce more power efficient circuits, however solutions using such approach still present gate-oxide overstress in some transistors. In this work a simple solution is presented which is shown to be able to overcome the problem. Moreover, simulations have shown that the proposed circuits can reach about 98.2% of voltage multiplication efficiency.