Noise analysis and characterization of a sigma-delta/capacitive microaccelerometer

Kulah H., Chae J., Yazdi N., Najafi K.

IEEE JOURNAL OF SOLID-STATE CIRCUITS, vol.41, no.2, pp.352-361, 2006 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 41 Issue: 2
  • Publication Date: 2006
  • Doi Number: 10.1109/jssc.2005.863148
  • Journal Name: IEEE JOURNAL OF SOLID-STATE CIRCUITS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.352-361
  • Keywords: capacitive readout, inertial sensors, microaccelerometers, micro-g, sigma-delta, switched capacitor, ACCELEROMETER, SURFACE
  • Middle East Technical University Affiliated: Yes

Abstract

This paper reports a high-sensitivity low-noise capacitive accelerometer system with one micro-g/root Hz resolution. The accelerometer and interface electronics together operate as a second-order electromechanical sigma-delta modulator. A detailed noise analysis of electromechanical sigma-delta capacitive accelerometers with a final goal of achieving sub-jig resolution is also presented. The analysis and test results have shown that amplifier thermal and sensor charging reference voltage noises are dominant in open-loop mode of operation. For closed-loop mode of operation, mass-residual motion is the dominant noise source at low sampling frequencies. By increasing the sampling frequency, both open-loop and closed-loop overall noise can be reduced significantly. The interface circuit has more than 120 dB dynamic range and can resolve better than 10 aF. The complete module operates from a single 5-V supply and has a measured sensitivity of 960 mV/g with a noise floor of 1.08 mu g/root Hz in open-loop. This system can resolve better than 10 mu g/root Hz in closed-loop.