A Neurostimulator for Deep Brain Stimulation With Wide Load Current and Impedance Adaptation Capability

Area of Science:

• Electrical Engineering
• Biomedical Engineering
• Microelectronics

Background:

• Current-controlled stimulators are crucial for various applications, but often struggle with adaptability to changing load impedances.
• Existing methods like Pulse Frequency Modulation (PFM) and Pulse Skip Modulation (PSM) have limitations in output dynamic range.

Purpose of the Study:

• To propose a biphasic and bipolar current-controlled stimulator with enhanced loading adaptability.
• To address overstress and reliability issues in high-voltage generator circuits.
• To improve the Power Conversion Efficiency (PCE) of the stimulator.

Main Methods:

• A novel Pulse Amplitude Modulation (PAM) loop control architecture was developed to drive the charge pump (CP), improving output dynamic range.
• A PAM-based Dual-Domain Voltage Scaling (PAM-DDVS) technique was introduced to minimize energy consumption.
• The stimulator was fabricated using TSMC 0.18μm 1.8V/3.3V process, integrating a high voltage generator, output driver, and an 8-bit current Digital-to-Analog Converter (DAC).

Main Results:

• The proposed stimulator demonstrates high loading adaptability, maintaining stimulus currents from 0.1mA to 20mA across a 0.5kΩ - 5kΩ impedance range.
• The novel PAM control architecture significantly enhances the output dynamic range compared to PFM and PSM.
• The PAM-DDVS technique effectively minimizes energy consumption while achieving a high adaptive range.

Conclusions:

• The developed current-controlled stimulator offers superior loading adaptability and power efficiency.
• The integrated chip addresses critical reliability concerns for high-voltage applications.
• The proposed techniques represent a significant advancement in stimulator design for improved performance and efficiency.