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Continuing from the last time, Xiao Yang sorted out the explanations of terms in the crystal oscillator circle yesterday. Today, I will share the second half. Please read it carefully~~
If you have any questions about crystal oscillators, you can also consult Xiao Yang to answer them for you···
10. Equivalent resistance
Equivalent resistance (ESR, Rr, R1), also known as resonant resistance. Under specified conditions, the resistance of a quartz crystal resonator at the resonant frequency without series load capacitance.
11. Excitation power level
The characteristic value of the power consumed by the crystal when it is working. The increase of the excitation level of the AT-cut crystal has a positive frequency change. Excessive excitation level will cause nonlinear effects, resulting in possible parasitic oscillation, severe thermal frequency drift, overstress frequency drift and resistance mutation. When the excitation level is too low, it will cause the oscillation resistance to be difficult to overcome, poor operation and unstable indicators.
12. Excitation level correlation
Also known as excitation level dependence, it is the effect of the resonant resistance of the crystal element changing with the excitation level conditions. When the excitation level applied to the crystal element changes, its resonant resistance also changes accordingly. This change generally has a certain regularity and can be expressed by the ratio of two resistances corresponding to two excitation levels. The expression is: DLD = Rr1/Rr2 (Rr1- is the resistance at a lower excitation level, and Rr2- is the resistance at a higher excitation level).
13. Insulation resistance
It refers to the resistance value between the pins of the crystal oscillator, or between the pins and the shell. In simple terms, it reflects the quality of the insulation performance inside the crystal oscillator. The larger the insulation resistance, the better the insulation performance of the crystal oscillator, the smaller the leakage current, and it can effectively prevent signal interference and electrical short circuits.
14. Fundamental frequency
The frequency generated by the crystal oscillator in the lowest-order vibration mode is also its "main vibration frequency".
The fundamental frequency is the most basic and main vibration frequency of the crystal oscillator, and other vibration modes (such as overtones) are based on multiples or derivatives of the fundamental frequency. The fundamental frequency determines the core operating frequency of the crystal oscillator.
15. Overtones
Overtones are high-order harmonic frequencies generated in the mechanical vibration of the crystal oscillator. Close to integer multiples of the fundamental frequency (such as 3 times, 5 times, 7 times, 9 times), etc., but not completely equal.
For example, the frequency of the 3rd overtone is close to 3 times the fundamental frequency, but slightly lower. The existence of overtones enables the crystal oscillator to operate at a higher frequency.
16. Equivalent circuit
The vibration of the quartz crystal resonator is essentially a mechanical vibration that can be measured by a two-terminal network with electronic conversion performance. This circuit includes L1 and C1, and C0 is incorporated into the circuit as a capacitor of a quartz crystal insulator. The impedance R1 related to elastic vibration is the resonant impedance of the quartz crystal resonator at the resonant frequency.
17. Negative impedance
Negative impedance refers to the impedance characteristics of the circuit at the oscillation frequency when looking from the two pins of the quartz crystal oscillator to the oscillation circuit. It is not a parameter of the crystal oscillator itself, but an important characteristic of the oscillation circuit. In order to improve the starting ability of the circuit, it is necessary to increase the negative impedance in the circuit. If the negative impedance is insufficient, the circuit may be difficult to start. Generally, the value of the negative impedance should reach 5-10 times the resonant impedance of the crystal oscillator to ensure stable operation of the circuit.
18. Annual aging rate
Measured in years, the relative change in the operating frequency of the crystal over time under specified conditions. The maximum frequency change is in the first month after the crystal frequency component is produced, and the frequency change over time will decrease. There are many reasons for this aging, such as: sealing characteristics and integrity, manufacturing process, material type, operating temperature and frequency.
