Fundamental or overtone? What are the factors that affect the frequency of crystal oscillator?
Fundamental or overtone? What are the factors that affect the frequency of crystal oscillator?
Crystal oscillator is a kind of passive electronic component which provides frequency signal. So, what factors affect the frequency crystal ?
First, from the perspective of the manufacturing process of crystal oscillator products, the output frequency crystal is directly related to the thickness of quartz wafer,
cutting angle and silver plating process. For the quartz wafer, the larger the thickness is, the lower the frequency crystalis. On the contrary, the thinner the wafer is,
the higher the crystal output frequency is. For example, SMD 3225-62.4mhz is much thinner than SMD 3225-12mhz.
In short, the core component of crystal oscillator is quartz chip, which generates stable and accurate mechanical vibration through piezoelectric effect characteristics.
Mechanical vibration generates the same frequency signal (we call it clock signal) to the clock chip, and the work of crystal oscillator is completed.
Because the material of quartz wafer is silicon dioxide, which is the same as that of glass, it is fragile. For the fundamental frequency and high frequency crystal,
in the process of transportation and use, too strong physical impact is easy to cause damage to the crystal oscillator with thin cr
ystal wafer, leading to crystal oscillator stop.
Therefore, in the production process, the general use of overtone technology to achieve the purpose of high-frequency output.
For example, a crystal oscillator with a fundamental frequency of 20.8mhz can get a frequency output of 62.4mhz after three overtones.
Generally, crystal oscillator above 40MHz is overtone.
What needs to be added is that the overtone crystal oscillator needs to match the overtone circuit.
In short, the fundamental frequency passive crystal oscillator only needs to match the appropriate external capacitor to work normally,
while the overtone crystal oscillator needs the combination of inductance and capacitor to generate overtone frequency.