Low-power signal processing methodologies for implantable biosensing platforms

This paper presents the design and implementation of highly-miniaturized, low-power CMOS signal conditioning schemes intended for use in a totally implantable biomedical sensor platform. Due to the thrust for the development implantable biomedical sensing systems for health management and disease prevention, there exists a need for signal processing schemes which occupy very little on-chip real estate and consume negligible amounts of power. In light of this, this paper presents both a CMOS current-to-frequency converter and voltage-to-frequency converter which have been designed primarily for use in implantable biosensing platforms and applications. Such designs can be implemented in stand-alone single sensor designs, or in tandem to create multi-analyte architectures. The versatility of employing current-to-frequency as well as voltage-to-frequency signal transduction schemes presents an avenue for the integration with any electrochemical sensing element which has been fabricated in an amperometric or voltammetric fashion. Furthermore, we demonstrate the efficacy of both these circuit designs by integrating them together with high performance electrochemical implantable glucose and pH sensors. The low power consumption and miniature size of the amperometric and voltammetric signal processing units (0.25 mm² and 18 μW / 0.045 mm² and 122 μW, respectively) presents an ideal design for signal processing in implantable continuous metabolic monitoring devices.