Compliant Stops for MEMS Inertial Device Drive PLL Stability

A MEMS inertial sensor device, method of operation, and fabrication process are described with a MEMS inertial sensor, drive actuation unit, drive measurement unit, and PLL circuit coupled together in operational engagement, where the MEMS inertial sensor includes a substrate, a proof mass positioned in spaced apart relationship above the substrate, a proof mass suspension member connected on a first end to the proof mass and connected on a second end to an anchor fixed to the substrate to enable the proof mass to laterally oscillate over the surface of the substrate, and a compliant stop structure positioned in relation to the proof mass suspension member to physically engage with lateral oscillating movement of the proof mass suspension member past a desired stroke travel distance without physically preventing lateral oscillating movement of the proof mass, thereby stiffening a spring stiffness measure of the proof mass suspension member.