In electronic devices, the choice of crystal oscillator and external components is critical to the performance, stability, and reliability of the system. Here are a few easy guides to choosing a crystal oscillator:
1. Determine the frequency range
When selecting a crystal oscillator, we need to determine the frequency range requirements of the system. Different applications have different frequency requirements, for example, a microcontroller may require a specific clock frequency, while a wireless communication module may require a specific RF frequency. Therefore, we need to ensure that the frequency range of the selected crystal oscillator can meet the needs of the system.
2. Select the appropriate crystal oscillator type
There are many types of crystal oscillators, each with its own unique characteristics and application scenarios. Such as quartz crystal resonator, ceramic resonator, temperature-compensated crystal oscillator, differential crystal oscillator, etc., according to the application requirements to choose the appropriate crystal oscillator type.
3. Consider accuracy and stability
The accuracy and stability of the crystal oscillator are critical to the performance of the system. Accuracy refers to the deviation between the output frequency of the crystal oscillator and the rated frequency, usually expressed in parts per million (ppm). Stability refers to the frequency deviation range of the crystal oscillator under environmental conditions such as temperature changes and power supply fluctuations, and is also usually expressed in ppm. Choose a crystal oscillator with sufficient accuracy and stability to ensure the timing of the system and the reliability of communication.
4. Consider the operating temperature range
Consider the operating environment conditions of the crystal oscillator. The operating temperature range of the crystal oscillator should match the operating temperature range of the system to ensure that the crystal oscillator can operate normally within the expected temperature range.
5. Select the appropriate load capacitor
Load capacitance is a necessary condition for the composition of an oscillating circuit. In the usual oscillation circuit, a quartz crystal resonator is used as an inductive reactance, while an oscillation circuit is used as a capacitive reactance. The load capacitance can be any value, but 10-30pf is preferable. The requirements for this capacitor are high, and NPO (C0G) capacitors are commonly used.
6. Select the appropriate vibration mode and cutting method
1.Vibration mode: The thickness shear oscillation mode has been widely used, except for 32In addition to the tuning fork vibration mode used for 768K crystals, the thickness shear vibration mode for other quartz crystals is adopted.
2.Cutting method: AT and BT cutting methods are mainly used for high frequency, and AT cutting methods are usually preferred because it has higher cutting accuracy and more stable cutting effect. In addition, the AT cutting method also has the advantages of fast processing speed, small cutting force, and small heat-affected zone.
7. Consider package size and pin type
Choose the right package size and pin type according to your actual application needs. For example, SMD packages are suitable for surface-mount processes, and for space-constrained applications, small packages may be more suitable.
8. Brand and business choice
Try to choose well-known brands of crystal oscillators and external components, these brands and manufacturers usually have more reliable quality assurance and longer service life, and can meet more stringent technical requirements and production standards. At the same time, choosing a well-known brand and a reputable supplier can also ensure that you receive high-quality after-sales service and technical support, which can help reduce maintenance costs and production downtime.
To sum up, the selection of crystal oscillator needs to comprehensively consider factors such as frequency range, crystal oscillator type, accuracy and stability, operating temperature range, load capacitance, vibration mode and dicing method, package size and pin type, and brand manufacturer.