A 0.0094mm2/Channel Time-Based Beat Frequency ADC in 65nm CMOS for Intra-Electrode Neural Recording

A digital-intensive, low-area, time-based ADC optimized for in-situ neural recording is fabricated in a 65nm test chip and validated with in-vivo data. The intrinsic inversely proportional gain of a beat frequency based quantizer allows recording of sub-millivolt neural signals without any sophisticated amplifiers or filters. A low-area analog-front-end (AFE) is implemented with a standard digital logic inverter transimpedance amplifier and tunable low pass and high pass filters. The test chip achieves 20.9dB SNDR for a 1mVpp input at 416Hz with a bandwidth of 4.2 kHz and consumes 52µW at 0.8V. In-vivo evoked potentials and spontaneous activity were measured directly from a mouse cerebellum without any external components, validating the efficacy of the aggressive tradeoffs. These results are achieved in an area of 0.0094mm2/channel, including on-chip AC coupling and filter passives, which makes this an attractive architecture for complete integration in ultra-high channel count neural recording systems.

[1]  Rms Noise.  ADC Input Noise: The Good, The Bad, and The Ugly. Is No Noise Good Noise? , 2006 .

[2]  Kyoungtae Lee,et al.  A 0.04-mm2 0.9-mW 71-dB SNDR distributed modular AS ADC with VCO-based integrator and digital DAC calibration , 2015, 2015 IEEE Custom Integrated Circuits Conference (CICC).

[3]  Sha Tao,et al.  A Power-Efficient Continuous-Time Incremental Sigma-Delta ADC for Neural Recording Systems , 2015, IEEE Transactions on Circuits and Systems I: Regular Papers.

[4]  Jose Silva-Martinez,et al.  A 4 Bit Continuous-Time $\Sigma \Delta $ Modulator With Fully Digital Quantization Noise Reduction Algorithm Employing a 7 Bit Quantizer , 2016, IEEE Journal of Solid-State Circuits.

[5]  Timothy J. Ebner,et al.  Abnormalities in the Climbing Fiber-Purkinje Cell Circuitry Contribute to Neuronal Dysfunction in ATXN1[82Q] Mice , 2011, The Journal of Neuroscience.

[6]  Chris H. Kim,et al.  Two-step beat frequency quantizer based ADC with adaptive reference control for low swing bio-potential signals , 2015, 2015 IEEE Custom Integrated Circuits Conference (CICC).

[7]  Refet Firat Yazicioglu,et al.  Time multiplexed active neural probe with 678 parallel recording sites , 2016, 2016 46th European Solid-State Device Research Conference (ESSDERC).

[8]  Wenlong Jiang,et al.  A ±50-mV Linear-Input-Range VCO-Based Neural-Recording Front-End With Digital Nonlinearity Correction , 2017, IEEE Journal of Solid-State Circuits.

[9]  Reid R. Harrison,et al.  The Design of Integrated Circuits to Observe Brain Activity , 2008, Proceedings of the IEEE.

[10]  Fernando Manuel Medeiro Hidalgo,et al.  A 515 nW, 0–18 dB Programmable Gain Analog-to-Digital Converter for In-Channel Neural Recording Interfaces , 2014, IEEE Transactions on Biomedical Circuits and Systems.

[11]  P. R. Troyk,et al.  Stimulus-resistant neural recording amplifier , 2003, Proceedings of the 25th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (IEEE Cat. No.03CH37439).

[12]  Chris H. Kim,et al.  A VCO-based ADC employing a multi-phase noise-shaping beat frequency quantizer for direct sampling of Sub-1mV input signals , 2014, Proceedings of the IEEE 2014 Custom Integrated Circuits Conference.

[13]  Refet Firat Yazicioglu,et al.  22.7 A 966-electrode neural probe with 384 configurable channels in 0.13µm SOI CMOS , 2016, 2016 IEEE International Solid-State Circuits Conference (ISSCC).