Synchronization of ultra-low power wireless sensor nodes

Radio activation in ultra-low-power wireless sensor nodes can require 5-6 orders of magnitude higher power than the sensor's average power consumption. Therefore, accurate timers that allow multiple sensor nodes to synchronize their radio communication are of critical concern for minimizing radio energy consumption. In this paper, we review ultra-low power timers and demonstrate their importance for the overall sensor node energy budget. We also propose a multistage gate-leakage-based timer with boosted charging and temperature compensation that reduces the synchronization uncertainty by 4.7× compared to the best prior gate-leakage-based timer with 660pW power consumption. Effective temperature sensitivity is reduced to 31ppm/°C.