Startup Time and Energy-Reduction Techniques for Crystal Oscillators in the IoT Era

The Internet-of-Things (IoT) radios are aggressively duty-cycled to reduce the average power consumption, but the startup time and energy of the crystal oscillator can limit their on-off latency and overall energy efficiency. In this brief, we provide a mathematical treatment of the startup time of the crystal oscillator and discuss the pros and cons of the recent startup time and energy-reduction techniques categorized as negative resistance boosting and energy injection.