A Wide-Dynamic-Range Neural-Recording IC With Automatic-Gain-Controlled AFE and CT Dynamic-Zoom  ADC for Saturation-Free Closed-Loop Neural Interfaces Y

Abstract

This article presents a neural-recording IC with automatic gain control (AGC) according to the input signal level. AGC enhances the dynamic range (DR) of the recording IC by more than 30 dB and allows it to take the benefits of the front-end amplification-based and direct-conversion-based recording struc- tures concurrently. By adaptively controlling the analog front-end (AFE) gain, the input-referred noise (IRN) of the overall system is greatly reduced while ensuring a wide DR. A continuous- time (CT) dynamic-zoom  ADC (CT-Zoom-ADC) is used for power-efficient two-step conversion. The coarse conversion output is reused for AGC, and the fine conversion resolution is adjusted adaptively by modifying the oversampling ratio according to the varying AFE gain. The presented neural-recording IC achieves 99.5-dB DR and 6.1- μV rms IRN over 5-kHz bandwidth, resulting in FoM DR of 185.2 dB, the effective number of bits (ENOB) Manuscript received 2 February 2022; revised 16 April 2022 and 23 June 2022; accepted 23 June 2022. Date of publication 15 July 2022; date of current version 26 September 2022. This article was approved by Associate Editor Shouyi Yin. This work was supported in part by the National Research and Development Program through the National Research Foundation (NRF) of Korea funded by the Ministry of Sc ience and ICT (MSIT), South Korea, under Grant 2020M3C1B8A01111568 and Grant 2021M3F3A2A01037365; in part by the DGIST Research and Development Program of the MSIT, South