A High-Resolution Accelerometer With Electrostatic Damping and Improved Supply Sensitivity

In this paper, a charge-balancing accelerometer is presented. A hybrid interface topology is utilised to achieve high resolution, high linearity and low power supply sensitivity. The accelerometer consists of a micromechanical sensor element, a self-balancing bridge (SBB) open-loop readout, AC force feedback and ΔΣ ADC. The SBB converts acceleration to ratiometric voltage. The ratiometric output of the SBB is converted to the digital domain by the ADC. In order to achieve high resolution, a micromechanical sensor element with a high quality factor, Q, is utilised. The AC force feedback is used for damping the high Q to get a low settling time. The sensor interface is fabricated in a standard 0.35 μm CMOS process. The fabricated chip has an area of 6.66 mm2 and consumes 1 mA at a nominal supply voltage of 3.6 V. The sensor has a maximum DC nonlinearity of 1.3% over the commercial temperature range with an input range of ±1.15 g. The noise floor of the sensor is around 2 μg/√{Hz} and the signal bandwidth is 200 Hz. The bias instability is 13 μ g and the sensor gain variation is less than 5% in the 3-3.6 V supply range.

[1]  Farrokh Ayazi,et al.  Micromachined inertial sensors , 1998, Proc. IEEE.

[2]  E. Hogenauer,et al.  An economical class of digital filters for decimation and interpolation , 1981 .

[3]  Erkka Laulainen,et al.  A Micropower $\Delta\Sigma$-Based Interface ASIC for a Capacitive 3-Axis Micro-Accelerometer , 2009, IEEE Journal of Solid-State Circuits.

[4]  T. Gabrielson.  Mechanical-thermal noise in micromachined acoustic and vibration sensors , 1993 .

[5]  L. Carley,et al.  Electromechanical ΔΣ modulation with high-Q micromechanical accelerometers and pulse density modulated force feedback. , 2006 .

[6]  Kari Halonen,et al.  A closed-loop SC interface for a ±1.4g accelerometer with 0.33% nonlinearity and 2µg/vHz input noise density , 2010, 2010 IEEE International Solid-State Circuits Conference - (ISSCC).

[7]  N. Yazdi,et al.  Noise analysis and characterization of a sigma-delta capacitive microaccelerometer , 2006, IEEE Journal of Solid-State Circuits.

[8]  Hanspeter Schmid,et al.  A 300Hz 19b DR capacitive accelerometer based on a versatile front end in a 5th-order ΔΣ loop , 2009, 2009 Proceedings of ESSCIRC.

[9]  L. Richard Carley,et al.  Electromechanical /spl Delta//spl Sigma/ modulation with high-Q micromechanical accelerometers and pulse density modulated force feedback , 2006, IEEE Transactions on Circuits and Systems I: Regular Papers.

[10]  F. Ayazi,et al.  A 2.5-V 14-bit /spl Sigma//spl Delta/ CMOS SOI capacitive accelerometer , 2004, IEEE Journal of Solid-State Circuits.

[11]  Gabor C. Temes,et al.  Circuit techniques for reducing the effects of op-amp imperfections: autozeroing, correlated double sampling, and chopper stabilization , 1996, Proc. IEEE.

[12]  Mikko Saukoski,et al.  A Micropower Front End for Three-Axis Capacitive Microaccelerometers , 2009, IEEE Transactions on Instrumentation and Measurement.

[13]  Erkka Laulainen,et al.  A Micropower �-Based Interface ASIC for a Capacitive 3-Axis Micro-Accelerometer , 2009 .

[14]  Kari Halonen,et al.  Continuous-time interface for a micromachined capacitive accelerometer with NEA of 4 μg and bandwidth of 300 Hz , 2009 .

[15]  Stefan Finkbeiner,et al.  MEMS for automotive and consumer electronics , 2013, 2013 Proceedings of the European Solid-State Device Research Conference (ESSDERC).

[16]  Huikai Xie,et al.  A Monolithic CMOS-MEMS 3-Axis Accelerometer With a Low-Noise, Low-Power Dual-Chopper Amplifier , 2008, IEEE Sensors Journal.

[17]  H. Leuthold,et al.  An ASIC for high-resolution capacitive microaccelerometers , 1990 .

[18]  K. Halonen,et al.  A micropower 2 MHz CMOS frequency reference for capacitive sensor applications , 2005, Proceedings of the 2005 European Conference on Circuit Theory and Design, 2005..

[19]  Kari Halonen,et al.  A charge balancing accelerometer interface with electrostatic damping , 2011, 2011 Proceedings of the ESSCIRC (ESSCIRC).

[20]  Xiaoji Niu,et al.  Analysis and Modeling of Inertial Sensors Using Allan Variance , 2008, IEEE Transactions on Instrumentation and Measurement.

[21]  Lasse Aaltonen,et al.  Linearity study of a self-balancing capacitive half-bridge sensor interface , 2010, 2010 12th Biennial Baltic Electronics Conference.

[22]  Kari Halonen,et al.  A Delta Sigma ADC for Low Power Sensor Applications , 2010 .

[23]  Kari Halonen,et al.  A ΔΣ ADC for low power sensor applications , 2010, Proceedings of 2010 IEEE International Symposium on Circuits and Systems.

[24]  P. Hurst,et al.  Double sampling in switched-capacitor delta-sigma A/D converters , 1990, IEEE International Symposium on Circuits and Systems.

[25]  Farrokh Ayazi,et al.  A 2.5V 14-bit ΣΔ CMOS-SOI capacitive accelerometer , 2004 .