Fully-Integrated System-In-Package device for drive, sense, and control of MEMS μmirrors for Raster Scan Projection

The System-In-Package here presented manages the movement of a couple of piezoelectric mu mirrors used for Raster Scan Projection applications. Its partitioning consists in two dice stacked one above the other. The first die works in the High Voltage domain and is responsible of the driving of the mirrors; it includes a single coil dual output boost converter that produces high voltage supplies (up to 45V). The linear driver that works up to 42V is composed by a low voltage DAC and a rail-to-rail push-pull output amplifier. The resonant driver, implementing a charge recovery architecture, translates a low voltage pulsing signal into a synchronous high voltage trapezoidal signal that excites the resonant mirror. The second die works in the low voltage domain to sense and control the mirrors movement. The PZR Wheatstone bridge, one for each mirror, is biased with a programmable voltage. Its differential output is applied to a read-out chain composed by a programmable Analog Front-End and a Continuous-Time Sigma Delta A/D Converter with 16-bits resolution. A fully integrated digital block processes the signals produced by the two sensing chains that are applied to their relative control loop algorithm. An additional front-end path is present to measure the PZR Bridge working temperature for sensitivity versus temperature compensation. Innovative lock-in and opening angle algorithms allows to control the movement of the resonant mu mirror against temperature, pressure and aging variations. Similarly, an innovative multi-feedback PID algorithm controls the linear mu mirror movement mainly suppressing the fundamental resonant component as well as other spurious modes.