A programmable charge-balanced current stimulation circuit for implantable medical devices

Active implantable medical devices (IMDs) require precise tissue stimulation to achieve effective therapeutic outcomes and ensure patient safety. This work introduces an 8-bit programmable current source, capable of delivering biphasic stimulation pulses from -25.5 mA to +25.5 mA in 0.1 mA steps, suitable for common IMD applications. The circuit supports pulses as short as a few microseconds, with measured settling times under 1 μs. The system includes a charge mismatch measurement circuit, and a 5-bit trimming mechanism to minimize the net charge delivered to the tissue. Fabricated in a 180 nm high-voltage CMOS technology, the circuit occupies less than 4 mm ², including a RISC-V processor, and I/O pads. Measurement results from the fabricated circuit are provided to validate the design.