1. The role of the crystal - the basic concepts of crystal
The crystal oscillator is a commonly used clock component in the circuit. The full name is called a crystal oscillator. It is made of a quartz crystal piece with a piezoelectric effect. Its role is to produce the original clock frequency, which is amplified or reduced by the frequency generator and becomes the various bus frequencies in the computer. Quartz resonators are used in household appliances and communication equipment because of their small size, light weight, high reliability, and high frequency stability. Quartz resonators are mainly used in resonant circuits where the frequency is very stable because they have extremely high frequency stability.
2. The role of crystal oscillator - the symbolic representation of the crystal oscillator
The crystal oscillator is structurally divided into a crystal oscillator of two feet and a crystal oscillator of three legs, and their representation patterns in the circuit are as shown in the following figure.
3. The role of the crystal - what are there?
The crystal operates in a resonant state with a crystal that converts electrical energy and mechanical energy into each other to provide stable, accurate single-frequency oscillation. Under normal working conditions, the ordinary crystal frequency has an absolute accuracy of 50%. Advanced precision is higher. Some crystal oscillators can also adjust the frequency within a certain range by the applied voltage, also known as voltage controlled oscillator (VCO).
The role of crystal oscillators is mainly divided into the following types:
1. Provide the basic clock signal to the system. Usually, one system shares a crystal oscillator to keep the parts in sync. Some communication systems use different crystal oscillators for the fundamental frequency and RF, and keep the synchronization by electronically adjusting the frequency.
2. The crystal is used in conjunction with a phase-locked loop circuit to provide the clock frequency required by the system. If different subsystems require clock signals of different frequencies, they can be provided by different phase-locked loops connected to the same crystal.
Knowledge Extension - How Crystals Work
The crystal oscillator is an abbreviation for crystal oscillator. It can be equivalently connected to a two-terminal network of a capacitor and a resistor in parallel and a capacitor in series, as shown in the figure below. Electrotechnically, this network has two resonance points. The lower frequency is the series resonance, and the higher frequency is the parallel resonance. Due to the characteristics of the crystal itself, the distance between the two frequencies is quite close. In this extremely narrow frequency range, the crystal oscillator is equivalent to an inductor, so as long as the crystal oscillator is connected in parallel with a suitable capacitor, it will form a parallel resonant circuit. . The parallel resonant circuit is added to a negative feedback circuit to form a sine wave oscillating circuit. Since the crystal oscillator is equivalent to a narrow frequency range of the inductor, even if the parameters of other components vary greatly, the frequency of the oscillator will not be a big change.
Knowledge Extension - Classification of Crystals
Crystal oscillators are also classified into passive crystals and active crystals.
Need passive crystal oscillator in the DSP chip connection method proposed in the datasheet. The passive crystal has no voltage problem, the signal level is variable, that is, it is determined according to the oscillation circuit. The same crystal can be applied to a variety of voltages, and can be used for a variety of different clock signal voltage requirements of the DSP . And the price is usually lower.
The active crystal oscillator does not require the internal oscillator of the DSP . The signal quality is good and stable, and the connection method is relatively simple, and no complicated configuration circuit is required.
4. The role of crystal oscillator - the application of crystal oscillator
The application field of crystal oscillator is very wide, and the four application fields of crystal oscillator.
First, mobile handheld devices: The most common mobile handheld devices are smart phones. In addition, Ipads, handheld game consoles, handheld POS machines, etc. are typical.
Second, consumer electronics: usually include laptops, cameras, cameras, headphones, stereos, tablets and so on.
Third, the communication network: in the communication network is usually divided into wired communication and wireless communication. The technical fields covered by wired communication include: optical transmission networks, data processing, connection functions, and the like. The technical fields covered by wireless networks typically include baseband, connection interfaces, radios, and the like.
Fourth, medical electronics: common medical electronic equipment includes: X-ray imaging, magnetic resonance imaging, ultrasound systems, endoscopes and so on.
The role of crystal oscillators - reference materials
1. Real-time calibration of the clock crystal
Description: Clock crystal error source and its real-time calibration
2. Why are some crystal oscillators three feet?
Description: Analysis of the type of crystal
3. Introduction of the maximum baud rate of the crystal oscillator and its error
Description: The maximum baud rate of the crystal oscillator and its error
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