When purchasing a crystal oscillator, you should first know what to look for. If you’re unsure about a product, it can take time and effort. Today, LCSC electronics supplier YXC brings valuable information to help you quickly learn about crystal oscillator purchasing. You can speed up your crystal oscillator purchasing skills and make your work more efficient!
Crystal Oscillator Verification Method
Quartz crystal resonators are certified based on the material number. There are differences in naming rules of the material number between crystal oscillator manufacturers. Therefore, you need to confirm whether the corresponding parameters of the material number are accurate before purchasing.
Crystal Oscillator Selection Requirements
Clock 32.768KHz crystal resonator package selection
Subject to the stability requirement, plug-in packaging (2*6, 3*8) is preferred, as the price is relatively advantageous. SMDs are expensive, have good stability, take up little space, and are suitable for automatic placement.
High-frequency crystal resonator packaging selection
On condition of low stability requirements, 49S or 49SMD packages are advantaged because of prices. SMD7.*5/SMD5*3.2/SMD3.2*2.5/SMD2*1.6 are much more expensive than the 49S series. Additionally, the 1.8432Mhz can only choose the 49U package.
Frequency deviation of quartz crystal resonator selection
It mainly includes adjusting frequency difference and temperature frequency difference. Usually, we select 10PPM and 20PPM.
Crystal oscillator nominal frequency selection
(1) 49S/SMD packaged crystals in AT cutting mode correspond to each frequency range.
- Fundamental frequency (Fundamental): Under a given shear vibration mode, the frequency range of the fundamental is within 3.2MHz~32MHz.
- Three overtone (3rd Overtone): Under a given shear vibration mode, the frequency range of the third overtone crystal is within 24MHz~80MHz.
- Fifth Overtone: Under a given shear vibration mode, the fifth overtone crystal frequency is over 80MHz.
(2) Package SMD1.2*1.0~ SMD7.0*5.0 crystal frequency selection reference table:
Package size frequency range (including passive and active)
| Package size | Frequency Range (passive and active) |
| SMD1210 | 32MHz-60MHz |
| SMD1612 | 1MHz-60MHz |
| SMD2016 | 1MHz-200MHz |
| SMD2520 | 1MHz-200MHz |
| SMD3225 | 1MHz-150MHz |
| SMD5032 | 1MHz-150MHz |
| SMD7050 | 1MHz-150MHz |
Crystal oscillator load capacitance selection
Load capacitance (CL) is a necessity when forming an oscillation circuit. The quartz crystal resonators serve as an inductive reactance in an oscillation circuit. While the oscillations function as a capacitive reactance. The relationship between load capacitance and resonant frequency is not linear. When the load capacitance is low, the frequency deviation is higher. When the load capacitance increases, the frequency deviation decreases. When the load capacitance in the oscillation circuit reduces, the resonant frequency deviation increases. Even a slight change in the circuit greatly affects the frequency stability. The load capacitance can be any value, but 10-30PF would be better. The requirements for this capacitor are relatively high, and it is customary to use capacitors made of NPO (C0G) material.
Crystal oscillator vibration mode selection:
The thickness-shear oscillation mode is widespread. The 32.768K crystal that utilizes the tuning fork vibration mode is an exception. All other quartz crystals adopt the thickness-shear vibration mode.
Crystal oscillator cutting method selection
High frequency typically employs the AT and BT cutting methods. In the industry, everyone usually uses the AT cutting method.
Crystal oscillator quality factors
Q value represents the quality factor during dynamic arm resonance in the equivalent circuit of a quartz crystal resonator. It directly impacts the maximum stability that an oscillation circuit can achieve. The higher the Q value, the smaller the impact of external reactance on the crystal. However, we cannot pursue a high Q value regardless of the cost.
Crystal oscillator static capacitor selection
Generally speaking, it is ≤7pf, which mainly affects the parallel resonant frequency fp.
Crystal oscillator operating temperature range selection
The commonly used operating temperature ranges are -20C~70C, -40°C~85°C, and -40°C~105°C. The temperature range considered normal is from -20°C to 70°C, whereas the wide temperature range is between -40°C and 85°C.
Crystal oscillator equivalent resistance selection
Usually the equivalent resistance is selected, except for special circuits where the equivalent resistance is not specified due to insufficient negative impedance.
Crystal oscillator excitation power selection
The optional values for the excitation level are 2mW, 1mW, 0.5mW, 0.2mW, 0.1mW, 50μW, 20μW, 10μW, 1μW, 0.1μW. Currently, the commonly used values are between 10μW~0.1mW.
Selection of annual aging rate
Annual aging rate is usually 3PPM/year and 5PPM/year.
ABOUT YXC
Shenzhen Yangxing Technology Co., Ltd. (YXC) specializes in designing RF clock chips and offering frequency device solutions.
Their primary offerings comprise programmable crystal oscillators, quartz MEMS oscillators, quartz crystal resonators, and Real-time clock (RTC). YXC products serve the automotive, communications, industrial, medical, and military markets. Their automotive products have been certified under the AEC-Q200 and IATF 16949 automotive systems.
Summarize
Purchasing a crystal oscillator is not a complicated matter. LCSC electronics has many types of Crystal Oscillator/Oscillator/Resonator for users to choose from. Users only need to know several main crystal oscillator parameters for their products, such as frequency, package size, load capacitance or voltage, operating temperature, and whether a specific brand is required. Users can conveniently make one-stop online purchases at LCSC Electronics, which saves a lot of purchasing time.
