ELECTRONICS Crystal vs oscillator – C
onsiderations might include how much space is available, frequency stability requirements, and component costs for developing this part of the circuit. Design engineers can build any oscillating circuit using a crystal – so why, even in simple applications like clock generation, are readily available oscillators often used? For small quantities, using a more expensive oscillator rather than a crystal may be recommendable to save on design costs. Using an oscillator will eliminate the requirement of certain additional external components required in a crystal circuit and might save space on the PCB. Oscillators are easily available in a variety of packages and microcontrollers usually contain information on how to apply an external oscillator in their manuals.
For larger quantities, or if an IC with internal oscillator is not being used, building an oscillating circuit with crystals and discrete components may be more economical. In which case a Pierce oscillator may be chosen, or an oscillator may be created by appropriate feedback of an inverter circuit. Most microcontrollers already contain the elementary components for the clock circuit, requiring only a crystal and other external passive components to complete the circuitry. The microcontroller application manuals should describe the necessary details.
There are other reasons for choosing an oscillator over a crystal. Oscillators are available in a wider range of frequencies and are often a choice for low or high frequencies where a certain footprint is required. Frequency stability may also be
which one for your circuit? When designing a new electronic circuit, design engineers need to consider whether a crystal or an oscillator is the best option.
important along with secured start-up conditions and reliability for specific environmental conditions important to the project. A Designer can choose between different types of oscillator – a TCXO, VCTCXO or VCXO – when compensation in temperature or voltage is required and where tight temperature tolerances are requested.
There are disadvantages too which need to be considered. The use of crystals requires certain efforts to adapt the circuit to the crystal and to secure a reliable start-up performance of the circuit. Whilst oscillators do not require external circuitry, as the capacitors and resistors are already incorporated in the devices, they are more sensitive to EMC, requiring Designers to follow certain HF design rules. Oscillators also require low power consumption. The GEYER Electronic Engineers have considered the break-even point at which a TCXO is better suited to a design than a crystal by looking at several use-case scenarios, concluding that TCXOs are typically better suited to meet temperature compensation and precision requirements
10 MAY 2025 | ELECTRONICS FOR ENGINEERS
where precise crystals might be chosen when cost remains a consideration. The full analysis and breakdown can be found in the GEYER Electronic White-paper ‘Crystal or TCXO Based Design – Where is the ‘Technical Break-Even?’, downloadable from the Design & Testcenter page at
www.geyer-electronic. com.
Whether a Designer chooses to use a crystal or an oscillator in his circuit, GEYER Electronic has more than 4000 components over 100+ product ranges to choose from, including a variety of ultra-miniature devices with tight specifications. If the exact specifications are not found in the portfolio, then the Design & Test Centre engineers in Munich can design a bespoke option for the project whilst offering full consultation, circuit validation, final testing and ongoing support for as long as is required. Visit
www.geyer-electronic.com to find out more about our products and Engineering services, including the GEYER Y-Quartz simulation app and Reference Design database, or email sales@geyer.
electronic.co.uk where the Geyer UK Team will be pleased to help.
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