A Fully Self-Contained Logarithmic Closed-Loop Deep Brain Stimulation SoC With Wireless Telemetry and Wireless Power Management

Although closed-loop deep brain stimulation (DBS) promises treatment of many neurological disorders, an implantable system-on-chip (SoC) implementing an effective closed-loop DBS algorithm has not been demonstrated. This work introduces a logarithmic, closed-loop DBS system that detects and processes low-frequency brain field signals to control and adapt stimulation currents. The system records and processes neural signals with four low-noise neural amplifier (LNA) channels, a multiplexed logarithmic ADC, and two high-pass and two low-pass digital logarithmic filters. Logarithmic processing saves power and achieves high dynamic range. A logarithmic domain digital signal processor (DSP) and PI-controller controls eight current stimulator channels and enables closed-loop stimulation. An RF transceiver, a clock generator, and a power harvester are also included in the system to achieve a complete implantable SoC. The 4 mm² 180 nm CMOS prototype consumes a total of 468 μW for recording and processing neural signals, for stimulation, and for two-way wireless communication.