Mixed-mode self-calibrated amplitude control scheme for MEMS vibratory gyroscopes

In this paper, a mixed-mode self-calibrated Automatic Gain Control (AGC) loop for MEMS applications is introduced. In MEMS-based vibratory gyroscope systems, an AGC is used to regulate the vibration amplitude of an inertia mass. Traditional analog AGCs suffer from a limited control range or bulky elements. Here, we present a low gain P-controller (Fine tuning) with digitally-controlled dynamic bias (Coarse tuning) for the AGC loop. The dynamic bias compensates for the low loop gain through the AGC and is generated using an error sense ADC. This approach achieves more than 9bits of uncalibrated oscillation amplitude accuracy over PVT without the need for trimming the gyroscope actuation gain. The power consumption of the designed main amplitude control circuitry is less than 200μW. The overall circuit was built using a standard 0.13μm CMOS technology.