Column: Design with frequency components
Crystals and oscillators: Engineering beyond specifi cations
In this series we will focus on the diff erent component types for timing, synchronization and frequency control, their basic parameters and how to best use them in various applications
By Daphne Popescu, Product and Sales Management, and Wendy Stewart, Sales and UK Offi ce Manager, GEYER Electronic
I
n this fi nal instalment of the series covering frequency source components, we have summarised the most important criteria regarding component selection and design rules, and added hidden limits of
oscillator design and examples underlining these limits. Electronic designs are many, and R&D
engineers are very creative, now having far more input sources for their designs than even just two years ago. In addition, the pace of technical evolution is continuously growing. Still, the focus in electronic board design is usually mainly on the MCU while the clock source is either neglected or chosen based on the recommendation in the catalogue of the IC manufacturer or from previous designs. Looking at diff erent aspects of designs
with crystals or oscillators, in Table 1 we have summarised the most important parameters and their impact.
Crystal physics beyond the datasheet From an engineering perspective, the real limits of oscillator design come from aspects such as: • Crystals are mechanical systems: Motional parameters, ESR, Q and frequency vary with temperature, ageing, drive-level and stress.
• Startup failures = lost margin: – Cold ESR increase + ageing + low drive erode negative resistance.
– Lab-proven designs fail in production when margins are too low.
10 March 2026
www.electronicsworld.co.uk Table 1: The most important parameters of crystals or oscillators
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