Abstract
A 1225-Channel Neuromorphic Retinal Prosthesis (RP) SoC is presented. Existing RP SoCs directly convert light intensity to electrical stimulus, which limit the adoption of delicate stimulus patterns to increase visual acuity. Moreover, a conventional centralized image processor leads to the local hot spot that poses a risk to the nearby retinal cells. To solve these issues, the proposed SoC adopts a distributed Neuromorphic Image Processor (NMIP) located within each pixel that extracts the outline of the incoming image, which reduces current dispersion and stimulus power compared with light-intensity proportional stimulus pattern. A spike-based asynchronous digital operation results in the power consumption of 56.3 nW/Ch without local temperature hot spot. At every 5×5 pixels, the localized (49-point) temperature-regulation circuit limits the temperature increase of neighboring retinal cells to less than 1°C, and the overall power consumption of the SoC to be less than that of the human eye. The 1225-channel SoC fabricated in 0.18μm 1P6M CMOS occupies 15mm2 while consuming 2.7 mW, and is successfully verified with image reconstruction demonstration.
Highlights
T HERE are over 2 million patients worldwide who suffer from retinitis pigmentosa [1] and 8 million US patients with age-related muscular degeneration (AMD) [2], [3]
This paper presents the Neuromorphic Retinal Prosthesis (NRP) SoC for dedicated and safe stimulation (Fig. 1(c)) [13]
The proposed NRP SoC is fabricated in a 0.18 μm 1P6M standard CMOS process, as shown in Fig. 13. 35 × 35 NMPIXELs area is similar to an active macular area (10 mm2), which can stimulate retinal cells efficiently
Summary
T HERE are over 2 million patients worldwide who suffer from retinitis pigmentosa [1] and 8 million US patients with age-related muscular degeneration (AMD) [2], [3] These patients cannot see due to the loss of their photoreceptors; they still have their inner retinal cells intact. Many works have focused on increasing the number of channels to improve the spatial resolution for better visual information, and [5] developed Alpha IMS with 1500-Ch and received CE approval in 2016. The visual acuity is still deficient due to the stimulation current dispersion within the human retina [1]–[5], which requires new technologies with a scaled number of channels. Considering the physiological power consumption of the human retina [6], the overall power consumption of the RP SoC should not exceed 3.4 mW in the worst-case scenario, which we can potentially power up the SoC using body-coupled power transfer [7], [8]
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