{"title":"A 101-dB DR 2.2GΩ-Input-Impedance Direct Digitization ExG Front-End With Δ-Modulation.","authors":"Yuying Li, Hao Li, Tianxiang Qu, Qi Liu, Zhiliang Hong, Jiawei Xu","doi":"10.1109/TBCAS.2025.3563304","DOIUrl":null,"url":null,"abstract":"<p><p>Long-term, continuous health monitoring imposes stringent demands on bio-recording analog front-end (AFE) circuits, specifically in terms of dynamic range (DR), noise, input impedance, and power consumption. This work introduces a DR-enhanced direct-digitization AFE based on a Δ-modulated transconductor (TC) stage, followed by a second-order ΔΣ ADC. In this architecture, the accumulated DAC is subtracted exclusively at the TC input stage, allowing the integrators to process only the low-amplitude Δ-modulated signal and thus relaxing the dynamic range constraints of conventional G<sub>m</sub>-C ΔΣ ADCs. The TC input stage achieves high input impedance and high linearity through a current-balancing transconductor and a flipped-voltage-follower (FVF) loop. Fabricated with a standard 180nm CMOS process, the proposed Δ-ΔΣ AFE exhibits an SNDR of 91 dB, a dynamic range of 101 dB, input referred noise of 58 nV/√Hz, and a power consumption of 63 μW. These results correspond to a FoMSNDR of 160.1 dB and a FoMDR of 170 dB. The AFE prototype has been validated through scalp EEG, leg EMG, and chest ECG with significant body movements, demonstrating its effectiveness as a motion-artifact-tolerant direct-ADC front end.</p>","PeriodicalId":94031,"journal":{"name":"IEEE transactions on biomedical circuits and systems","volume":"PP ","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"IEEE transactions on biomedical circuits and systems","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1109/TBCAS.2025.3563304","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Long-term, continuous health monitoring imposes stringent demands on bio-recording analog front-end (AFE) circuits, specifically in terms of dynamic range (DR), noise, input impedance, and power consumption. This work introduces a DR-enhanced direct-digitization AFE based on a Δ-modulated transconductor (TC) stage, followed by a second-order ΔΣ ADC. In this architecture, the accumulated DAC is subtracted exclusively at the TC input stage, allowing the integrators to process only the low-amplitude Δ-modulated signal and thus relaxing the dynamic range constraints of conventional Gm-C ΔΣ ADCs. The TC input stage achieves high input impedance and high linearity through a current-balancing transconductor and a flipped-voltage-follower (FVF) loop. Fabricated with a standard 180nm CMOS process, the proposed Δ-ΔΣ AFE exhibits an SNDR of 91 dB, a dynamic range of 101 dB, input referred noise of 58 nV/√Hz, and a power consumption of 63 μW. These results correspond to a FoMSNDR of 160.1 dB and a FoMDR of 170 dB. The AFE prototype has been validated through scalp EEG, leg EMG, and chest ECG with significant body movements, demonstrating its effectiveness as a motion-artifact-tolerant direct-ADC front end.