Hybrid On-Chip Clocking for Sensor Nodes

Spencer Kellis,  Nathaniel Gaskin,  Bennion Redd,  Richard Brown

University of Utah


On-chip clock generation has become an attractive alternative to external quartz oscillators for low-power sensing systems. LC and ring oscillators typically use less power, and can start and stop much faster than traditional quartz oscillators, allowing systems to spend more time in low-power sleep states. A hybrid on-chip clocking scheme is proposed in which a ring oscillator is used as the reference clock for digital processing, and an LC oscillator is used when a more stable, accurate reference is needed for digital communication. Simulations show that the fast wakeup capabilities of the hybrid clock scheme lead to more than 80% reduced power compared to a system using a crystal reference clock source. The on-chip clock generators of the WIMS series of microsystems are presented as a functional implementation of the proposed hybrid clock scheme.