AN-1051 Calibration Methods for Silego GreenCLKs

GreenCLK technology is a silicon circuit which allows a 32.768 kHz clock to be produced with good accuracy and low power. The technology avoids the poor over-temperature and aging characteristics of 32.768kHz tuning fork crystals, by leveraging high accuracy sources such as AT-cut crystals and TCXO’s to generate the 32.768kHz clock. For example, it can replace the 32.768 kHz crystals in the notebook computer by using the high-accuracy (typically 25MHz) crystal already present in such systems. High accuracy frequency sources can consume significant power, but GreenCLK technology can eliminate this issue with an ultra-low power Hibernate Mode which only turns on the frequency source periodically at very low duty cycle while still accomplishing internal calibration of the 32.768kHz clock. So even if a high power (mA) MHz TCXO is used, the effective average overall current consumption can be reduced to sub-uA levels. Note that a 32.768KHz TCXO, though it initially compensates for temperature variation, still has a 32.768kHz tuning fork crystal at it’s core with their inherent aging issues. GreenCLK being based on low-aging sources thus allows for calibration methods to be effective.

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