A Circuit System Design for Implantable Multi-channel neural stimulator
More than 161 million people worldwide are suffering from ablepsia [1], and among them, ten million are blind result from the photoreceptor loss due to degenerative retinal diseases. For these patients, neural stimulating proved to be an effective method
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NTRODUCTION Artificial vision based on a rehabilitative device replacing defective photoreceptors in blind people appears in many aspects a most reliable choice for us to achieve the patients a better vision, and optical nerve prosthesis with penetrating multi-electrode arrays [4]. This device includes three major modules: Radio Frequency Module, Wireless Power Providing Module and Neural Stimulation Module (Figure 1). The Radio Frequency Module includes CCD camera, Image Acquisition & Processing Unit and Communication Unit. The Neural Stimulation Module includes Multi-channel neural stimulator, and Communication Unit. First, the CCD camera receives stimulations from light, and then information is processed via a image processing unit. A communication module transports visual data from extra ocular modules to intraocular modules via RF technique. Neural stimulation module first converts digital signals to analogy signals and then generates stimulation current on optic afferent nerves.
Wireless Power Providing Module offers energy for intraocular modules. Multi-channel neural stimulator visual data are transmitted by RF inductively to the intraocular unit which in turn recovers the data and sets the charge balanced bipolarity stimulation for the retina via electrodes. MCU receives the signal and passes it with particular format to the DAC. When the 8-channal signals are stored in the registers of DAC, the MCU controls the DAC to perform to drive the after circuits to generate 8-channels currents at the same time. There are several formidable challenges in designing an implantable, safe, efficient multi-channel neural stimulator. To meet the need of these requirements, the system owns four salient characters. First of all, the size must be small enough to be implantable. To balance the quality and the dimension, we decide the dimension of our design at 36mm*28mm finally. Secondly, to protect the body implanted with the neural stimulator from assembling excessive charge, we use bipolarity (anodic and cathodic) and symmetrical current as our stimulating current. Thirdly, the normal neural potential is at the level of µA, so the current that the circuit generates is limited at the level of µA too. To generate stable and accurate current, we choose exact amplifiers and ADC to perform the current generation. At last, we use 8-channal currents to stimulate the retinal nerve simultaneously to get more efficient result.
Radio Frequency Module Image Acquisition & Processing Unit
Communication Unit
Neural Simulation Module
Communication Unit
Multi-channel neural stimulator
Power CLASS-E Amplifier Unit
Rectification Circuit Unit
Wireless Power Providing Module
Fig. 1 schematic figure of artificial vision
Yi Peng, Xiaohong Weng (Eds.): APCMBE 2008, IFMBE Proceedings 19, pp. 58–61, 2008 www.springerlink.com © Springer-Verlag Berlin Heidelberg 2008
A Circuit System Design for Implantable Multi-channel neural stimulator
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II. THE CIRCUIT OF IMPLANTABLE MULTI-CHANNEL NEURAL STIMULATOR
A. The architecture and working p
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