18.2 A fully-implantable cochlear implant SoC with piezoelectric middle-ear sensor and energy-efficient stimulation in 0.18μm HVCMOS

A cochlear implant (CI) is a device that electrically stimulates the auditory nerve to restore hearing in people with profound hearing loss. Conventional CIs rely on an external unit comprising a microphone and sound processor to pick up and encode sound. The external unit raises concerns with social stigma and limits usage in the shower or during water sports, motivating the need for a fully-implantable (i.e., invisible) cochlear implant (FICI). The limited energy storage capacity of the implanted system requires low-power (<;1mW total power) sound processing and auditory nerve stimulation to enable operation from an implanted battery that is wirelessly recharged only once daily. Recent state-of-the-art ICs are typically designed for external microphone-based CIs and do not require the neural stimulator to be on the same chip [1]. Prior implantable acoustic sensors such as accelerometers sense the sound-induced vibration of the middle ear, but this approach has limited sensitivity and requires several mW of power for the sensor itself [2].