Design and In-Vivo Verification of a CMOS Bone-Guided Cochlear Implant Microsystem

Objective: To develop and verify a CMOS bone-guided cochlear implant (BGCI) microsystem with electrodes placed on the bone surface of the cochlea and the outside of round window for treating high-frequency hearing loss. Methods: The BGCI microsystem consists of an external unit and an implanted unit. The external system-on-chip (SOC) is designed to process acoustic signals through an acquisition circuit and an acoustic DSP processor to generate stimulation patterns and commands that are transmitted to the implanted unit through a 13.56 MHz wireless power and bidirectional data telemetry. In the wireless power te-lemetry, a voltage doubler/tripler (2X/3X) active rectifier is used to enhance the power conversion efficiency and generate 2 V and 3 V output voltages. In the wireless data telemetry, phase-locked loop (PLL) based binary phase-shift keying (BPSK) and load-shift keying (LSK) modulators/demodulators are adopted for the down-link and uplink data through high-Q coils, respectively. The im-planted chip with 4-channel high-voltage-tolerant stimulator gen-erates biphasic stimulation currents up to 800 μA. Results: Electri-cal tests on the fabricated BGCI microsystem has been performed to verify the chip functions. The in-vivo animal tests in guinea pigs have shown the evoked third wave (Wave eIII) of electrically evoked auditory brainstem response (EABR) waveforms. It is ver-ified that auditory nerves can be successfully stimulated and acoustic hearing can be partially preserved. Conclusion and Significance: Different from traditional cochlear implants, the pro-posed BGCI microsystem is less invasive, preserves partially acoustic hearing, and provides an effective alternative to treating high-frequency hearing loss.