A 4-Channel Neural Stimulation IC Design With Charge Balancing and Multiple Current Output Modes

Area of Science:

• Biomedical Engineering
• Integrated Circuit Design
• Neural Stimulation

Background:

• Neural stimulation requires precise control over current output waveforms.
• Minimizing power consumption and maximizing stimulation pulse duration are critical for implantable devices.
• Ensuring patient safety through effective charge management is paramount.

Purpose of the Study:

• To design and implement a versatile neural stimulation integrated circuit (IC) with multiple current output modes.
• To enhance power efficiency and extend stimulation pulse duration using an exponential current decay.
• To incorporate a robust charge balancing technique for safe multi-mode neural stimulation.

Main Methods:

• Developed a neural stimulation IC with independently selectable exponential and square wave outputs for cathodic and anodic phases, creating four stimulation modes.
• Integrated an exponential current generation circuit to minimize headroom voltage and increase pulse duration.
• Implemented a charge balancing technique to mitigate residual charge accumulation across all operation modes.

Main Results:

• The four-channel stimulator IC, fabricated in a 180-nm CMOS process, achieved a maximum power efficiency of 91.3%.
• The maximum stimulation duration was extended to 3 times that of previous works.
• Residual charge in exponential output mode was minimized to 255 pC per cycle, with rapid charge removal (<60 μs) and stable electrode voltage.

Conclusions:

• The proposed neural stimulation IC offers enhanced performance in terms of power efficiency and stimulation duration.
• The integrated charge balancing technique effectively minimizes residual charge, ensuring patient safety.
• This design represents a significant advancement for implantable neural stimulators requiring flexible and safe operation.