The design of cmos electrode-Tissue impedance measurement circuit using differential current switch with cmfb bias for implantable neuro-modulation socs

Chi Wei Huang*, Chi Heng Chung, Ruei Syuan Syu, Chung Yu Wu

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

A new electrode-Tissue impedance measurement circuit integrated with a System-on-Chip (SoC) is proposed and designed for implantable medical devices to monitor the electrode-Tissue contact status. In the proposed circuit, a differential step current is injected into the electrode-Tissue structure to generate a voltage. A differential current switch with a common-mode feedback (CMFB) bias circuit and shaped control signals are designed to generate accurate step currents and stable common-mode bias voltage. Moreover, the measurement circuit shares part of the bio-signal acquisition circuit in the SoC. Thus only an extra power dissipation of 4.3μW is needed at the operating frequency of 15.625Hz. The proposed circuit is fabricated by 0.18 um CMOS technology. The measurement results have shown that the resolution is 17 pp and the maximum error is 3.4% for an impedance of 46k. The proposed circuit is also verified in an in-vitro test by measuring the electrode-Tissue impedance of a subdural grid electrode sunk in the phosphate buffered saline (PBS) buffer.

Original languageEnglish
Title of host publicationBioCAS 2019 - Biomedical Circuits and Systems Conference, Proceedings
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781509006175
DOIs
StatePublished - Oct 2019
Event2019 IEEE Biomedical Circuits and Systems Conference, BioCAS 2019 - Nara, Japan
Duration: 17 Oct 201919 Oct 2019

Publication series

NameBioCAS 2019 - Biomedical Circuits and Systems Conference, Proceedings

Conference

Conference2019 IEEE Biomedical Circuits and Systems Conference, BioCAS 2019
CountryJapan
CityNara
Period17/10/1919/10/19

Keywords

  • CMFB bias circuit
  • differential current switch
  • impedance measurement
  • implantable medical systems
  • in-vitro test
  • low power
  • step current

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    Huang, C. W., Chung, C. H., Syu, R. S., & Wu, C. Y. (2019). The design of cmos electrode-Tissue impedance measurement circuit using differential current switch with cmfb bias for implantable neuro-modulation socs. In BioCAS 2019 - Biomedical Circuits and Systems Conference, Proceedings [8919039] (BioCAS 2019 - Biomedical Circuits and Systems Conference, Proceedings). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/BIOCAS.2019.8919039