A 32-ch Neuromodulator with redundant Voltage Monitors avoiding Blocking Capacitors

Neural recording and modulation has evolved rapidly in recent years. Closed-loop neuromodulation systems have been successfully demonstrated for the treatment of Parkinson's disease and epilepsy. Chronically implanted medical devices, requiring compliance to rigorous safety regulations, employ numerous safety measures to protect the patient. One such measure to prevent direct current from being applied to the tissue in case of a system failure is typically the usage of external blocking capacitors between the electrodes and the neuromodulator. These capacitors can cause significant magnetic resonance imaging (MRI) magnetic susceptibility artifacts that appear as a shading effect. This paper presents some of the challenges which arise when evolving neuromodulation hardware from benchtop prototypes to biomedical systems for chronic implantation in humans. We propose a novel safety measure to mitigate the MRI shading issue while still complying to the relevant safety regulations. Furthermore, we propose several additional features that improve the flexibility and usability of a 32-channel neuromodulation platform. The neuromodulator was fabricated in a 180 nm HV CMOS process and realizes a fully digital-to-neural interface.