TY - JOUR
T1 - A Bidirectional Neural Interface IC With Chopper Stabilized BioADC Array and Charge Balanced Stimulator
AU - Greenwald, Elliot
AU - So, Ernest
AU - Wang, Qihong
AU - Mollazadeh, Mohsen
AU - Maier, Christoph
AU - Etienne-Cummings, Ralph
AU - Cauwenberghs, Gert
AU - Thakor, Nitish
N1 - Funding Information:
This work was supported by the NIH grant RO1HL071568 to N. Thakor and the NSF EFRI-M3C grant 1137279 to G. Cauwenberghs. E. Greenwald was supported in part by NIH training grant 5T32EB003383. This paper was recommended by Associate Editor A. Basu.
Publisher Copyright:
© 2016 IEEE.
PY - 2016/10
Y1 - 2016/10
N2 - We present a bidirectional neural interface with a 4-channel biopotential analog-to-digital converter (bioADC) and a 4-channel current-mode stimulator in 180 nm CMOS. The bioADC directly transduces microvolt biopotentials into a digital representation without a voltage-amplification stage. Each bioADC channel comprises a continuous-time first-order ΔΣ modulator with a chopper-stabilized OTA input and current feedback, followed by a second-order comb-filter decimator with programmable oversampling ratio. Each stimulator channel contains two independent digital-to-analog converters for anodic and cathodic current generation. A shared calibration circuit matches the amplitude of the anodic and cathodic currents for charge balancing. Powered from a 1.5 V supply, the analog and digital circuits in each recording channel draw on average 1.54 μA and 2.13 μA of supply current, respectively. The bioADCs achieve an SNR of 58 and a SFDR of >70 dB, for better than 9-b ENOB. Intracranial EEG recordings from an anesthetized rat are shown and compared to simultaneous recordings from a commercial reference system to validate performance in-vivo. Additionally, we demonstrate bidirectional operation by recording cardiac modulation induced through vagus nerve stimulation, and closed-loop control of cardiac rhythm. The micropower operation, direct digital readout, and integration of electrical stimulation circuits make this interface ideally suited for closed-loop neuromodulation applications.
AB - We present a bidirectional neural interface with a 4-channel biopotential analog-to-digital converter (bioADC) and a 4-channel current-mode stimulator in 180 nm CMOS. The bioADC directly transduces microvolt biopotentials into a digital representation without a voltage-amplification stage. Each bioADC channel comprises a continuous-time first-order ΔΣ modulator with a chopper-stabilized OTA input and current feedback, followed by a second-order comb-filter decimator with programmable oversampling ratio. Each stimulator channel contains two independent digital-to-analog converters for anodic and cathodic current generation. A shared calibration circuit matches the amplitude of the anodic and cathodic currents for charge balancing. Powered from a 1.5 V supply, the analog and digital circuits in each recording channel draw on average 1.54 μA and 2.13 μA of supply current, respectively. The bioADCs achieve an SNR of 58 and a SFDR of >70 dB, for better than 9-b ENOB. Intracranial EEG recordings from an anesthetized rat are shown and compared to simultaneous recordings from a commercial reference system to validate performance in-vivo. Additionally, we demonstrate bidirectional operation by recording cardiac modulation induced through vagus nerve stimulation, and closed-loop control of cardiac rhythm. The micropower operation, direct digital readout, and integration of electrical stimulation circuits make this interface ideally suited for closed-loop neuromodulation applications.
KW - Chopper stabilization
KW - Delta-Sigma
KW - closed-loop neuromodulation
KW - electrocorticography
KW - electroencephalogram
KW - neural recording
KW - vagus nerve stimulation
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U2 - 10.1109/TBCAS.2016.2614845
DO - 10.1109/TBCAS.2016.2614845
M3 - Article
C2 - 27845676
AN - SCOPUS:84995466220
SN - 1932-4545
VL - 10
SP - 990
EP - 1002
JO - IEEE Transactions on Biomedical Circuits and Systems
JF - IEEE Transactions on Biomedical Circuits and Systems
IS - 5
M1 - 7738450
ER -