Energy-efficient neural stimulation system design for implantable medical devices

Implantable medical devices for neural stimulation have received great attention in biomedical applications to restore or modulate sensory and motor function. Many miniaturized implants rely on wireless power transfer, where deliverable power is limited and the on-chip supply becomes time-varying under coil misalignment and link activity. At the same time, wide electrode-tissue interface (ETI) variability complicates compliance, efficiency, and long-term charge balance, making a highly efficient and safe stimulator essential. This paper surveys neural stimulation architectures by organizing prior work into current-controlled stimulation (CCS), voltage-controlled stimulation (VCS), and switched-capacitor stimulation (SCS). For CCS and VCS, we discuss adaptive energy-delivery techniques that reduce headroom loss and monitoring/correction approaches that enforce charge safety under ETI variation. For SCS, we highlight charging-interface and residual-management strategies, as well as discharge-based stimulus families, that strongly influence end-to-end efficiency and stimulation efficacy under tight power budgets.