A Lossless Neural Recording SoC for Epilepsy Monitoring with up to 84.9-dB Dynamic Range and Rail-to-Rail Stimulation Artifact Tolerance

Next-generation closed-loop epilepsy management system should be able to flag both the onset and termination of the ictal phase of repeated seizures, so that the neural stimulation profile can be tailor made to align to the optimal time frame for the best therapeutic outcomes. However, the presence of stimulation artifact (SA) makes it a significant challenge in implementing such a closed-loop system which requires concurrent recording of neural signals and stimulation of certain brain regions. High dynamic range (DR) is an important requirement for neural amplifiers to ensure lossless recording. We propose a high DR, rail-to-rail artifact tolerant system-on-a-chip (SoC). In the absence of SA, the SoC records and quantifies neural signals with low power consumption. When a stimulation artifact is detected, an additional ADC and a DAC are used to sample and reconstruct the artifact signal, respectively. The reconstructed artifact is then fed to the input of a differential amplifier as a common-mode signal for artifact removal. The target neural signal can subsequently be extracted by an independent component analysis algorithm. The technique has been verified using X-Fab’s 0.18-µm CMOS process. The simulation result suggests the power consumptions with and without artifact suppression are 15.6 and 46.5 µW, respectively. The input dynamic range of the SoC can be extended to 84.9-dB when an SA is detected.