Column: Design with frequency components
• Drive level is a non-linear trade-off : – Too high: frequency driſt and accelerated ageing.
– Too low: higher ESR, startup risk.
• Stability is oſt en stress-limited: PCB bend, soldering, coatings shiſt frequency more than temperature.
• Ageing is front-loaded and design- dependent: – Largest driſt occurs early. – High drive, thermal cycling and stress dominate long-term behaviour.
• Hidden modes exist: Spurious resonances and activity dips cause fi eld- only failures.
• Phase noise is system-defi ned: Circuit loading, pulling and drive reduce the eff ective Q. Ultimately, the R&D takeaway is that design margin and physics understanding matter more than datasheet compliance. It permits you to predict startup failures, design realistic margins, improve phase noise without changing components, justify higher-grade crystals when necessary, and reduce failure returns. T ese aspects are oſt en neglected if designs must be fast, cheap and not explicitly mentioned in technical documents.
Design examples We have chosen some simple examples, showing potential error sources linked to the R&D aspects presented before and possible countermeasures; see on the right.
Design and testing are critical Even a “perfect” design on paper can fail in real systems because crystals and oscillators are mechanical-electrical systems aff ected by temperature, ageing, stress and manufacturing variation. Robust design alone is not enough – only combined with upfront simulation, e.g. with a design APP, and comprehensive testing across worst-case conditions (cold, hot, aged parts, mechanical stress, load capacitance variation, and so on) ensures reliable startup, phase noise and long-term stability.
T is instalment is the last in the series. Webinar on this topic is scheduled for March 4th, 2025 – see our website for details:
www.electronicsworld.co.uk
www.electronicsworld.co.uk March 2026 11
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