VLSI potentiostat array for distributed electrochemical neural recording

A neurochemical sensor system is being developed to spatially sense and process neurotransmitters. This paper reports the design and VLSI implementation of a multichannel potentiostat that interfaces to a nitric-oxide (NO) sensor array. Picoampere to microampere input currents are range-normalized with programmable gain, and digitized by a bank of current-mode delta-sigma analog-to-digital (A/D) converters. First-order noise shaping and 4096-fold oversampling provide high signal-to-noise ratio for the low-frequency NO transients. A shift register scans the buffered decimated delta-sigma outputs in bit-serial format providing asynchronous sequential readout. An 8-channel potentiostat in 0.5 μm CMOS measures 1.5 mm×1.5 mm, and consumes 0.5 mW power. The device is expected to serve as a valuable tool for neurophysiological research and implantable neural prostheses.