JSTS:Journal of Semiconductor Technology and Science

The Institute of Electronics and Information Engineers (대한전자공학회)
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A Digital Readout IC with Digital Offset Canceller for Capacitive Sensors

  • Lim, Dong-Hyuk (School of Electrical Engineering and Computer Science, Seoul National University) ;
  • Lee, Sang-Yoon (School of Electrical Engineering and Computer Science, Seoul National University) ;
  • Choi, Woo-Seok (School of Electrical Engineering and Computer Science, Seoul National University) ;
  • Park, Jun-Eun (School of Electrical Engineering and Computer Science, Seoul National University) ;
  • Jeong, Deog-Kyoon (School of Electrical Engineering and Computer Science, Seoul National University)
  • Received : 2011.11.11
  • Published : 2012.09.30
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Abstract

A digital readout IC for capacitive sensors is presented. Digital capacitance readout circuits suffer from static capacitance of sensors, especially single-ended sensors, and require large passive elements to cancel such DC offset signal. For this reason, to maximize a dynamic range with a small die area, the proposed circuit features digital filters having a coarse and fine compensation steps. Moreover, by employing switched-capacitor circuit for the front-end, correlated double sampling (CDS) technique can be adopted to minimize low-frequency device noise. The proposed circuit targeted 8-kHz signal bandwidth and oversampling ratio (OSR) of 64, thus a $3^{rd}$-order ${\Delta}{\Sigma}$ modulator operating at 1 MH was used for pulse-density-modulated (PDM) output. The proposed IC was designed in a 0.18-${\mu}m$ CMOS mixed-mode process, and occupied $0.86{\times}1.33mm^2$. The measurement results shows suppressed DC power under about -30 dBFS with minimized device flicker noise.

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References

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Cited by

  1. Reduction of Common Mode Noise and Global Multivalued Offset in Touch Screen Systems by Correlated Double Sampling vol.12, pp.6, 2016, https://doi.org/10.1109/JDT.2016.2515847
  2. Integrated microelectronic capacitive readout subsystem for lab-on-a-chip applications vol.25, pp.5, 2014, https://doi.org/10.1088/0957-0233/25/5/055702