Analysis of sense finger dynamics for accurate ΣΔ MEMS accelerometer modelling in VHDL-AMS

The sense finger dynamics in the capacitive MEMS accelerometer affect the performance of electromechanical mixed-domain Sigma-Delta control loop. Correct behaviour can not be correctly predicted by conventional lumped model of the mechanical sensing element. This contribution presents an improved distributed mechanical model implemented in VHDL-AMS and detailed analysis of how sense finger dynamics affect the operation of the accelerometer when the system is subjected by jolt and step excitations. Such excitations are common in typical MEMS accelerometer applications in automobile safety systems.