ABSTRACT
Digital circuits and systems have been a part of modern life, whether in the form of digital signal processors, processors, or application-specific integrated circuits. The considered systems operate down to near-threshold voltages and low frequencies to fit within highly constrained power budgets. This chapter describes the design strategies elaborated along the clock chain. It explains the typical topology of a low-power microcontroller system and introduces the clocking requirements. The chapter focuses on the most power-constrained digital systems, for Internet of Things (IoT) applications. These systems assume different detailed architectures depending on their use cases, which range from miniaturized implantable biomedical sensors to industrial machine diagnosis application, or the most commonly known personal IoT. After highlighting the design considerations related to time references in low-power digital systems, the chapter draws on some fundamental frequency and time metrology metrics.
