Transient dynamics of a MEMS variable capacitor driven with a Dickson charge pump

In the actuation of electrostatically controlled capacitive MEMS devices, drive voltages over the supply voltage are commonly required. In order to obtain such voltages, charge pumps are often used. This paper presents and discusses two methods to drive capacitive MEMS devices using IC-compatible Dickson charge pumps designed to minimize power consumption. Drive circuits include voltage shaping to minimize charge injection in order to provide better reliability. The main design constraints to integrate them in state of the art IC technologies are identified and quantified. The required charge pumps are also optimized to provide an efficient use of its total capacitance. The transient dynamics of charge pumps connected to a RF MEMS variable capacitor are also analysed and discussed. Finally, the proposed methods are tested and validated through experimental results.