Safety ensuring retinal prosthesis with precise charge balance and low power consumption

Area of Science:

• Biomedical Engineering
• Neuroscience
• Electrical Engineering

Background:

• Safe neural stimulation is critical for medical devices like retinal prostheses.
• Key safety concerns include zero-net charge transfer and heat generation in tissues.
• Existing stimulators require precise electrical performance for tissue safety.

Purpose of the Study:

• To present a novel neuro-stimulator for retinal prostheses.
• To ensure safe neural stimulation by achieving precise charge balancing and low power consumption.
• To mathematically derive the required matching accuracy for safe biphasic current pulses.

Main Methods:

• Development of a safety-ensuring neuro-stimulator using a 0.35 μm high voltage (HV) CMOS process.
• Implementation of a dynamic current mirror for accurate charge balancing.
• Mathematical derivation of biphasic current pulse matching accuracy.
• Experimental validation using a resistor-capacitor electrode model.

Main Results:

• The proposed stimulator achieved less than 30 nA DC current flow into tissue across a wide stimulation range (32 μA-1 mA) without shorting.
• With shorting enabled, DC current flow was further reduced to 1.5 nA.
• Low power consumption was achieved, with less than 30 μW consumed in stand-by mode.

Conclusions:

• The developed neuro-stimulator effectively ensures safe neural stimulation for retinal prostheses.
• Precise charge balancing and low power consumption are achieved through innovative circuit design.
• The findings contribute to the advancement of safe and efficient neural stimulation technologies.