Main Application of Epson Programmable Crystal Oscillator Resonator

Quartz crystal resonators are mainly used in frequency control and frequency selection circuits.

1. The relationship between vibration modes and frequencies:

Base Frequency 1-35MHz

3 overtones 10-75 MHz

Five overtones 50-150 MHz

Seven overtones ranging from 100 to 200 MHz

Nine overtones 150-250MHz

2. Crystal resistance: For the same frequency, when working in high overtone vibration, its resistance value will be greater than when working in low vibration. The function of "signal source + level meter" is completed by network analyzer

Ri, R0: Instrument internal resistance: generally 50_

R1 - Outer impedance of input terminal of filter, impedance value is matched impedance minus 50_.

R2 - Output impedance of filter output, impedance value is matched impedance minus 50_.

3. The influence of excitation level: Generally speaking, the increase of excitation level of AT-cut crystal has a positive frequency change. Excessive excitation level will cause non-linear effect, which may lead to parasitic oscillation; severe thermal frequency drift; over-stress frequency drift and resistance mutation. When the excitation level is too low, the starting resistance is not easy to overcome, the work is not good and the index is unstable.

4. Load capacitance and frequency traction: In many applications, it is necessary to use a load reactance element to tract the crystal frequency. In most cases, the load reactance is capacitive. When the capacitance value is CL, the relative load resonance frequency offset is DL=C1/[2(C0+CL)]. When CL is used as adjustable element from DL1 to DL2, the relative frequency traction is DL1, L2= C1 (CL1-CL2)/[2 (C0+CL1) (C0+CL2)].

5. Selection of load capacitance: When the crystal works at the fundamental frequency, the standard values of load capacitance are 20PF, 30PF, 50PF and 100PF. The overtone crystal often works in series resonance. Where the load capacitance is used, the load capacitance should be selected from the following standard values: 8PF, 12PF, 15PF, 20PF and 30PF.

6. Working temperature range and temperature frequency difference: When proposing temperature frequency difference, the temperature rise tolerance caused by equipment operation should be considered. When the requirement of temperature frequency difference is very high and space and power are allowed, constant temperature operation should be considered. The constant temperature crystal oscillator is designed for this purpose.

7. Application of filter circuit: When applied to filter circuit, besides the usual regulations, more attention should be paid to the value and error of equivalent circuit elements, as well as the position and magnitude of parasitic response. Because of the particularity of filter crystal design, users should specify when choosing and purchasing.