A variable range bi-phasic current stimulus driver circuitry for an implantable retinal prosthetic device

This paper reports a driver circuitry to generate bi-phasic (anodic and cathodic) current pulses for stimulating the retinal layer through electrodes which is part of a retinal prosthetic device for implants in blind patients affected by retinitis pigmentosa (RP) and age-related macular degeneration...

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Bibliographic Details
Published in:IEEE journal of solid-state circuits 2005-03, Vol.40 (3), p.763-771
Main Authors: Sivaprakasam, M., Wentai Liu, Humayun, M.S., Weiland, J.D.
Format: Article
Language:English
Subjects:
Applied sciences
Architecture
Biomedical
Chips
Circuit properties
CMOS technology
Design. Technologies. Operation analysis. Testing
Device driver programs
Driver circuits
Electric circuits
Electric potential
Electric, optical and optoelectronic circuits
Electrodes
Electronic circuits
Electronics
Exact sciences and technology
functional electrical stimulation (FES)
implantable devices
Implants
Integrated circuits
Macular degeneration
microstimulator
Patients
Pigmentation
Prostheses
Prosthetics
Pulse circuits
Pulse generation
Retina
retinal prosthesis
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Signal convertors
Voltage
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Summary:This paper reports a driver circuitry to generate bi-phasic (anodic and cathodic) current pulses for stimulating the retinal layer through electrodes which is part of a retinal prosthetic device for implants in blind patients affected by retinitis pigmentosa (RP) and age-related macular degeneration (AMD). Dual voltage architecture is used to halve the number of interface leads from the chip to the stimulation sites compared to a single voltage supply. The driver circuitry is designed to deliver currents with six bit resolution for a wide range of full scale currents up to 600 /spl mu/A. To cater to the varying stimulus requirements among patients and different regions of the retina, variable gain architecture is used to achieve fine resolution even for a narrow range of stimulus. 1:8 demultiplexing feature is embedded within the output stage thus allowing one DAC for eight outputs. A novel charge cancellation circuitry with current limiting capability is implemented to discharge the electrodes for medical safety. Measurement results of a prototype chip fabricated in 1.5-/spl mu/m CMOS technology are presented.
ISSN:0018-9200
1558-173X
DOI:10.1109/JSSC.2005.843630