Precision readout circuits for capacitive microaccelerometers

This paper presents a review of capacitive readout front-end circuits for high-precision accelerometers. The primary design parameters and the trade-offs affecting the resolution are presented. The discussions apply to all capacitive microsensor interfaces. Also, a high-sensitivity capacitive accelerometer interface circuit for hybrid-integration with a surface/bulk micromachined micro-g accelerometer is described. The first generation of the circuit resolves 75 aF of capacitance on /spl sim/120 pF parasitic capacitance with a 200 kHz sampling rate, and the second generation resolves 20 aF with 1 MHz sampling rate. The overall sensor-circuit module has a noise floor of 1.6 /spl mu/g//spl radic/Hz at ambient atmosphere.

[1]  T. A. Core,et al.  A low cost monolithic accelerometer , 1992, 1992 Symposium on VLSI Circuits Digest of Technical Papers.

[2]  Bernhard E. Boser,et al.  A three-axis micromachined accelerometer with a CMOS position-sense interface and digital offset-trim electronics , 1999, IEEE J. Solid State Circuits.

[3]  N. Wongkomet,et al.  Correlated double sampling in capacitive position sensing circuits for micromachined applications , 1998, IEEE. APCCAS 1998. 1998 IEEE Asia-Pacific Conference on Circuits and Systems. Microelectronics and Integrating Systems. Proceedings (Cat. No.98EX242).

[4]  N. Yazdi,et al.  An interface IC for a capacitive silicon /spl mu/g accelerometer , 1999, 1999 IEEE International Solid-State Circuits Conference. Digest of Technical Papers. ISSCC. First Edition (Cat. No.99CH36278).

[5]  G. Fedder,et al.  A Low-Noise Low-Offset Capacitive Sensing Amplifier for a 50-g = Hz Monolithic CMOS MEMS Accelerometer , 2004 .

[6]  S. Sherman,et al.  Single-chip surface-micromachined integrated gyroscope with 50/spl deg//hour root Allan variance , 2002, 2002 IEEE International Solid-State Circuits Conference. Digest of Technical Papers (Cat. No.02CH37315).

[7]  N. Yazdi,et al.  11. 6 A Multi-Step Electromechanical Σ∆ Converter for Micro-g Capacitive Accelerometers , 2003 .

[8]  G.K. Fedder,et al.  A low-noise low-offset capacitive sensing amplifier for a 50-/spl mu/g//spl radic/Hz monolithic CMOS MEMS accelerometer , 2004, IEEE Journal of Solid-State Circuits.

[9]  Khalil Najafi,et al.  A generic interface chip for capacitive sensors in low-power multi-parameter microsystems , 2000 .

[10]  Stephen F. Bart,et al.  An Integrated Force-balanced Capacitive Accelerometer For Low-G Applications , 1995, Proceedings of the International Solid-State Sensors and Actuators Conference - TRANSDUCERS '95.

[11]  S. Sherman,et al.  Single-chip surface micromachined integrated gyroscope with 50°/h Allan deviation , 2002, IEEE J. Solid State Circuits.

[12]  K. Najafi,et al.  An all-silicon single-wafer micro-g accelerometer with a combined surface and bulk micromachining process , 2000, Journal of Microelectromechanical Systems.

[13]  Roger T. Howe,et al.  Surface micromachined, digitally force-balanced accelerometer with integrated CMOS detection circuitry , 1992, Technical Digest IEEE Solid-State Sensor and Actuator Workshop.