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A Noise-Reduced Light-to-Frequency Converter for Sub-0.1% Perfusion Index Blood SpO2 Sensing.
- Source :
- IEEE Transactions on Biomedical Circuits & Systems; Oct2020, Vol. 14 Issue 5, p931-941, 11p
- Publication Year :
- 2020
-
Abstract
- To improve the SpO<subscript>2</subscript> sensing system performance for hypoperfusion (low perfusion index) applications, this paper proposes a low-noise light-to-frequency converter scheme from two aspects. First, a low-noise photocurrent buffer is proposed by reducing the amplifier noise floor with a transconductance-boost (g<subscript>m</subscript>-boost) circuit structure. Second, a digital processing unit of pulse-frequency-duty-cycle modulation is proposed to minimize the quantization noise in the following timer by limiting the maximum output frequency. The proposed light-to-frequency sensor chip is designed and fabricated with a 0.35- μm CMOS process. The overall chip area is 1 × 0.9 mm<superscript>2</superscript> and the typical total current consumption is about 1.8 mA from a 3.3-V power supply at room temperature. The measurement results prove the proposed functionality of output pulse duty cycle modulation, while the SNR of a typical 10-kHz output frequency is 59 dB with about 9-dB improvement when compared with the previous design. Among them, 2–3 dB SNR improvement stems from the gm-boosting and the rest comes from the layout design. In-system experimental results show that the minimum measurable PI using the proposed blood SpO<subscript>2</subscript> sensor could be as low as 0.06% with 2-percentage-point error of SpO<subscript>2</subscript>. The proposed chip is suitable for portable low-power high-performance blood oximeter devices especially for hypoperfusion applications. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 19324545
- Volume :
- 14
- Issue :
- 5
- Database :
- Complementary Index
- Journal :
- IEEE Transactions on Biomedical Circuits & Systems
- Publication Type :
- Academic Journal
- Accession number :
- 146472479
- Full Text :
- https://doi.org/10.1109/TBCAS.2020.3010362