ABSTRACT
This paper presents a fully integrated low-power neuron recording front-end system in TSMC 65 nm 1p6m CMOS technology. The proposed system is comprised of two recording modules, each containing 32 recording channels with tunable bandwidth and gain, a 32-to-1 multiplexer, one differential successive approximation register (SAR) analog-to-digital converter (ADC) with programmable sampling rate on each channel, and a digital control module to govern the signal digitization as well as to encode and serialize the digitized neuron signal from two ADCs. The recording amplifier presents a low power and low noise merits of 6 µW and input-referred noise of 3.8 µV(rms). The ADC digitizes the neural signal at a sampling rate of 40 kS/s with 9-bit resolution. The overall power consumption of the entire system is 2.56 mW and occupies an area of 3 × 4mm(2).
Subject(s)
Equipment Design , Neurons/physiologyABSTRACT
Epiretinal prostheses deliver electrical pulses through a great number of stimulation electrodes to generate visual perception. Since a large amount of stimulation parameters have to be sent into the eye wirelessly, the transmission efficiency and data loss are critical design factors. While the error rate of wireless transmission might not be perfect due to the limited power dissipation allowed in the eyeball, data loss can be reduced by altering the size of data packets. In this paper, the correlation between packet length and data loss are analyzed, and we find that more than 10 times of reduction in data loss can be achieved by shortening the data packets. The costs and benefits of using error-correcting codes (ECC) are also evaluated. A data packet protocol for 1024-channel retinal prosthesis as well as the corresponding receiver circuitry are then designed based on the results of the analyses. The circuit occupies 330 µm × 262 µm using 0.18 µm CMOS technology. With the flexibility provided by the protocol and receiver circuitry, data packet configuration (size and ECC on/off) can be adaptively adjusted to optimize for real-time wireless channel error conditions.
