Digital electronics for inertial MEMS and space applications

This paper presents an electronic platform for driving resonant MEMS in inertial sensors, and possibly other resonant or carrier based sensors. The architecture is fully integrated in a digital programmable device (FPGA), and avoids several critical components when dealing with space qualification. The core hardware functions are Direct Digital Synthesis , Sigma-Delta modulation, Time to Digital conversion. These functions are driven by an embedded processor, managing a second level of software functions : synchronous demodulation, Phase-Locked Loop, decimation, digital communications. The specificity of this digital platform is to avoid usual Analog-To- Digital and Digital-To-Analog conversion. All measurements are performed by means of digital delay counting, yet allowing an interesting resolution of 16 bits even on carried signals up to 100 kHz with a frequency resolution better than 1 μHz (11 digits on the frequency). A prototype of vibrating accelerometer has been integrated and characterized to experience the electronic performance on a real sensor. The results show that the embedded architecture is already close to the performance obtained with separate equipments on the test bench.