A wireless power interface for rechargeable battery operated neural recording implants

Area of Science:

• Electrical Engineering
• Biomedical Engineering
• Microelectronics

Background:

• Implantable neural recording microsystems require efficient wireless power solutions.
• Miniature Li-ion batteries are crucial for powering these devices.
• Existing wireless charging systems face challenges in efficiency and accuracy.

Purpose of the Study:

• To develop an integrated analog front-end for wireless powering and recharging of Li-ion batteries in neural recording microsystems.
• To improve the efficiency and accuracy of wireless battery charging.
• To reduce the complexity and component count of the charging circuit.

Main Methods:

• Utilized Schottky barrier contact diodes for efficient DC signal extraction.
• Implemented a novel control loop for battery charging, enabling simultaneous constant-current and constant-voltage operation.
• Minimized reliance on external components like current sense resistors.
• Leveraged bulk CMOS technology for circuit fabrication.

Main Results:

• Achieved end-of-charge detection accuracy of +/- 1.3% (or +/-20 microA) under worst-case conditions.
• Demonstrated simultaneous constant-current and constant-voltage charging.
• The integrated circuit occupies 1.735 mm(2) with a power dissipation of 8.4 mW.
• Attained a charging efficiency of 73% at 1.5 mA load current and 4.1 V.

Conclusions:

• The developed analog front-end offers a highly accurate and efficient solution for wireless battery recharging in implantable devices.
• The novel control loop simplifies the charging architecture and enhances performance.
• This technology is well-suited for miniaturized neural recording microsystems, paving the way for improved implantable devices.