Implementation of an all-digital electrostatic micro-mirror controller

Electrostatically-actuated micro-mirrors are used in a range of applications such as pico-projectors, laser scanners, and micro-spectrometers. For precise operation of these devices, accurate control of output frequency and amplitude is needed. An all-digital micro-mirror controller was designed using a single photodiode feedback technique, phase locked loop frequency control, duty cycle amplitude control, and dithering fractional-N divider for fine frequency adjustment. The controller was initially tested on an FPGA and subsequently implemented as an ASIC on the XFab XT018 process. This process allowed the integration of the 200 V high voltage amplifier required to operate the electrostatic micro-mirror. The implemented controller was successfully tested with a 21 kHz micro-mirror at its resonant point and with controlled amplitude.