Challenges and constraints in designing implantable medical ICs

Implantable medical electronics are differentiated from most of the other electronic-system implementations by their unique combination of extreme low-power and high-reliability requirements. Many implanted medical devices rely on a fixed nonrechargeable battery over their entire lifetime. These constraints elevate power management and budgeting within the integrated circuits (ICs) to key system-design parameters. So much so, in fact, that the requirements drive not only differences in circuit design, but also place a number of constraints on the design environment and design tools, manufacturing processes, and targets used to implement those designs, test methodologies, and the fundamental understanding into the physics of failure. These constraints often make standard offerings available from the wafer foundries, electronic-design-automation (EDA) suppliers, and commercial third-party IP providers unviable without some level of modification. A successful design often requires process changes and monitoring to ensure low-static-current drain, digital-cell-library optimization with synthesis tools for low-power power-efficient memory design, weak-inversion analog design, accurate low-power models, and test visibility. As system complexity and activity rise, without a proportional increase in available energy, these challenges grow more persistent.