Recent advances in integrated circuit (IC) technology, as well as innovations in circuit design techniques, have led to systems with processing capabilities that can supplement, or even entirely replace, complex biomedical operations such as speech spectral analysis. Importantly, however, with the right technical approach, this functionality can be achieved at power levels and form factors allowing these systems to be entirely implantable. Indeed the processing capabilities of ICs are virtually unlimited, but energy, in biomedical electronics, is highly limited. For example, if an implanted medical device were powered by a low-power general purpose processor, which consumes approximately 10 mW, current battery technology would accommodate approximately 3 days of operation. Alternatively, dedicated solutions, employing specialized low-power design techniques, consume approximately 8 μW, achieving more than 10 years of operation with the same battery (1).
A conceptual diagram for a generic biomedical device appears in Figure 1. The core components of the device are shown, which include data conversion, signal processing, and communication subsystems, and these interface with the biomedical environment through sensors and actuators. Additionally, an energy subsystem is required to efficiently power the electronics. This review focuses on the core electronic components and the energy subsystem, describing the specialized techniques required to achieve ultralow-energy operation for practical biomedical systems.