The role of a resistor in parallel with a crystal oscillator circuit
Preface
When designing a circuit, we usually see some external high-speed crystal oscillators connected in parallel with a 1MΩ resistor, but we find that some circuits can work normally without using them. Are you curious about this?
The circuit diagram is as follows:
In fact, the crystal oscillator circuit can start to oscillate normally without a 1M resistor in parallel during operation, but there will be a running lag.
Therefore, connecting a 1MΩ resistor in parallel can help the crystal oscillator start to oscillate. When the program starts slowly or does not run, in this case, connecting a 1MΩ resistor in parallel to the crystal oscillator can solve the problem.
The function of this resistor:
1. Make the device originally a logic inverter work in the linear region and obtain gain.
2. Increase the negative impedance in the circuit, increase the gain, and reduce the crystal oscillator start-up time.
3. Increase the stability of the oscillation circuit.
4. Current limiting to prevent resonator fluctuations.
All in all, its function is to pave the way for a stable and rapid rise.
Note: There is a problem with the selection of this resistor value.