A robust semi-digital readout method for crosstalk elimination in resonant sensors

A novel readout method for resonant sensors that is easily implemented in a digital CMOS process and that efficiently eliminates parasitic crosstalk between the excitation signal and the detection circuitry is presented. The readout method utilizes a semi-digital excitation scheme that lacks a second harmonic, which is the frequency of the driving force, and thus the oscillation frequency of the sensor. The method has the advantage that it is more accurately generated, controlled and adjusted than the previously used sinusoidal excitation signal. The novel readout method has been evaluated by the design of an excitation and detection ASIC manufactured in the 0.8 μm CMOS CXQ process of AMS (Austria Micro Systems). Characterization of the functionality and the performance of the manufactured ASIC shows excellent agreement with the theory.