Crystal oscillator is a crystal oscillator. It mainly provides a highly stable time frequency signal for the circuit so that electronic components can work uniformly. How is this achieved?
1. Working principle of crystal oscillator
It turns out that the traditional LC oscillator has poor stability and the frequency of the AC signal it generates is easy to change, so later a special component, a quartz crystal, was added to the oscillator. The quartz crystal can produce a highly stable signal, so it is called this kind of quartz oscillator. The oscillator of a crystal is called a crystal oscillator, or crystal oscillator.
The crystal oscillator has a piezoelectric effect, that is, the crystal will deform when a voltage is applied to the two poles of the chip. Conversely, if an external force deforms the chip, the metal sheets on the two poles will generate voltage. If an appropriate alternating voltage is applied to the wafer, the wafer will resonate (the resonant frequency is related to the inclination angle of the quartz bevel, etc., and the frequency is constant). The crystal oscillator uses a crystal that can convert electrical energy and mechanical energy into each other. Working in a resonance state can provide stable and accurate single-frequency oscillation. Under normal working conditions, the absolute accuracy of the ordinary crystal oscillator frequency can reach 50 parts per million.
2. The difference between active crystal oscillator and passive crystal oscillator
Crystal oscillators are divided into active crystal oscillators and passive crystal oscillators. They have certain differences in pins and oscillators.
The active crystal oscillator has 4 pins and is a complete oscillator. In addition to the quartz crystal, there are also transistors and resistor-capacitor components. It depends on the circuit you apply. If there is a clock circuit, use passive. Otherwise, use passive Active. The passive crystal oscillator is a non-polar component with 2 pins. It requires the help of a clock circuit to generate an oscillation signal and cannot oscillate by itself.
Active crystal oscillators do not require the internal oscillator of the DSP, the signal quality is good, relatively stable, and the connection method is relatively simple (mainly to filter the power supply, usually using a PI filter network composed of capacitors and inductors, and a small resistor at the output A resistor of high value can filter the signal), and no complicated configuration is required.
Passive crystals need to use the oscillator inside the DSP chip. Passive crystals have no voltage problems. The signal level is variable, which means it is determined by the oscillator circuit. The same crystal can be applied to a variety of voltages. Available for a variety of DSPs with different clock signal voltage requirements, and are generally less expensive.
Since the quartz crystal oscillator has very good frequency stability and the ability to resist external interference, the quartz crystal oscillator is used to generate the reference frequency. The accuracy of the frequency in the circuit is controlled by the reference frequency. The application range of quartz crystal oscillators is very wide, and their quality levels and frequency accuracy also vary greatly. Most of the signal sources (oscillation sources) of signal generators used in communication systems also use quartz crystal oscillators.Keywords: 4G network IO controller