A 200-Channel Area-Power-Efficient Chemical and Electrical Dual-Mode Acquisition IC for the Study of Neurodegenerative Diseases

Microelectrode array (MEA) can be used in the study of neurodegenerative diseases by monitoring the chemical neurotransmitter release and the electrical potential simultaneously at the cellular level. Currently, the MEA technology is migrating to more electrodes and higher electrode density, which raises power and area constraints on the design of acquisition IC. In this paper, we report the design of a 200-channel dual-mode acquisition IC with highly efficient usage of power and area. Under the constraints of target noise and fast settling, the current channel design saves power by including a novel current buffer biased in discrete time (DT) before the TIA (transimpedance amplifier). The 200 channels are sampled at 20 kS/s and quantized by column-wise SAR ADCs. The prototype IC was fabricated in a 0.18
$\mu{\rm m}$
CMOS process. Silicon measurements show the current channel has 21.6
${\rm pA}_{\rm rms}$
noise with cyclic voltammetry (CV) and 0.48
${\rm pA}_{\rm rms}$
noise with constant amperometry (CA) while consuming 12.1
$\mu{\rm W}$
. The voltage channel has 4.07
$\mu{\rm V}_{\rm rms}$
noise in the bandwidth of 100 kHz and 0.2% nonlinearity while consuming 9.1
$\mu{\rm W}$
. Each channel occupies 0.03
${\rm mm}^{2}$
area, which is among the smallest.