27.3 A 3-axis open-loop gyroscope with demodulation phase error correction

Consumer-electronic (CE) gyroscopes have recently enjoyed broad deployment in high-volume applications, largely due to intuitive user interfaces in smart phones and video game controllers. For their continued expansion into more demanding CE applications, a further reduction of their noise, offset drift, and power dissipation, especially in the emerging always-on category, is mandatory. To be viable, solutions to these conflicting requirements must overcome the challenges of low cost and ever-shrinking package size. This paper describes one such solution with special emphasis on offset drift reduction. The system presented here discards the standard practice of electrically cancelling the quadrature error, and instead combines information derived from continuously monitoring the quadrature error together with a single-point temperature calibration to reduce offset drift. This paper presents the architecture and circuits used to realize a 3-axis open-loop gyroscope with a one-sigma TCO of 0.0065°/s/K.