A linear high voltage charge pump for MEMs applications in 0.18/spl mu/m CMOS technology

Tunable MEMS components start to appear in wireless communication systems. They allow for new functionality such as tunable RF filters or they improve performance like electrostatically tuned variable capacitors that are used in voltage-controlled oscillators. However, the required tuning voltage for these capacitors is often much higher than the supply voltage of these capacitors is often much higher than the supply voltage of the deep sub-micron (Bi)CMOS technology which is typically used for these applications. Therefore we designed a high voltage charge pump that can generate an output voltage between -0.7V and +14.8 V out of a 1.8 V power supply. It is built in a 0.18 /spl mu/m CMOS technology, requires the same control signals as a regular charge pump and provides a constant output current of 0.7/spl mu/A over its complete voltage range of MEMS variable capacitors at low power, at a small area cost and in a way which is completely transparent to the system designer.