A 3-Axis Gyroscope for Electronic Stability Control With Continuous Self-Test

A three-axis automotive gyroscope ASIC for electronic stability control (ESC) with noise density that is less than 0.004 degrees /s/ root Hz in a 80 Hz bandwidth and an offset drift lower than +/- 0.1 degrees/s over the automotive temperature range -40 to 140 degrees C, without any temperature compensation, is reported. A closed-loop, force-feedback architecture along with electromechanical quadrature cancellation enables the low noise and low offset-drift performance. The application of this work needs to meet the ASIL-D automotive safety standard which requires the highest level of automotive safety. Therefore, this work also presents a low-overhead approach for implementing accurate continuous safety monitoring to monitor defects, which can develop in the field, and can give rise to a false output. To achieve this, two test signals are injected into the quadrature cancellation loop to traverse the entire signal path. The system is clocked by a low-phase noise PLL, which allows the coexistence of the test signals and the measured signal in close proximity, without a noise penalty. The architecture of the drive loop is chosen to not only achieve low-phase noise but also robustness to parasitic mechanical modes of the sensor.