A High TCMRR, Inherently Charge Balanced Bidirectional Front-End for Multichannel Closed-Loop Neuromodulation

This paper describes a multichannel bidirectional front-end for implantable closed-loop neuromodulation. Stimulation artefacts are reduced by way of a 4-channel H-bridge current source sharing stimulator front-end that minimizes residual charge drops in the electrodes via topology-inherent charge balancing. A 4-channel chopper front-end is capable of multichannel recording in the presence of artefacts as a result of its high total common-mode rejection ratio (TCMRR) that accounts for CMRR degradation due to electrode mismatch. Experimental verification of a prototype fabricated in a standard 180 nm process shows a stimulator front-end with 0.059% charge balance and 0.275 nA DC current error. The recording front-end consumes 3.24 µW, tolerates common-mode interference up to 1 Vpp and shows a TCMRR > 66 dB for 500 mVpp inputs.Ministerio de Economía y Competitividad TEC2016-80923-POffice of Naval Research (USA) N00014111031

Integrated circuit design for implantable neural interfaces

Progress in microfabrication technology has opened the way for new possibilities in neuroscience and medicine. Chronic, biocompatible brain implants with recording and stimulation capabilities provided by embedded electronics have been successfully demonstrated. However, more ambitious applications call for improvements in every aspect of existing implementations. This thesis proposes two prototypes that advance the field in significant ways. The first prototype is a neural recording front-end with spectral selectivity capabilities that implements a design strategy that leads to the lowest reported power consumption as compared to the state of the art. The second one is a bidirectional front-end for closed-loop neuromodulation that accounts for self-interference and impedance mismatch thus enabling simultaneous recording and stimulation. The design process and experimental verification of both prototypes is presented herein