Delta-Sigma Control of Dielectric Charge for Contactless Capacitive MEMS

In this paper, we present a new closed-loop control method of dielectric charge for contactless capacitive microelectromechanical systems. The method uses a feedback loop to maintain the net charge in the dielectric layer at the desired level. We show that, under particular conditions, the control loop is similar to a thermal sigma-delta modulator as used in thermal sensors. In this way, the control actuation will inject an average charge into the dielectric to keep it at a desired level while applying an actuation bit stream to compensate the charge being continuously leaked out of the dielectric. The validation of the method is carried out employing numerical simulation and experimental measurements of Poly-MUMPS devices.