Things you don’t know about crystal oscillators, applications of crystal oscillators with different frequencies + crystal oscillator circuit

For the crystal oscillator, the editor has brought many articles. The introduction of crystal oscillators in this article will be based on two aspects: 1. The application of crystal oscillators with different frequencies, and 2. The introduction of crystal oscillator circuits. If you have some interest in the two crystal oscillator issues that this article will discuss, you may wish to continue reading.

Crystal oscillators are used a lot in Electronic circuits, their name is crystal resonators, and they can play different roles in circuits. For example, we can see more than one in some single-chip circuits and computer motherboards. Frequency crystal oscillators can also be seen in color TV remote controls. We found that these crystals have almost the same shape, but the frequencies identified by their appearance are different. Let’s take a look at the applications of crystal oscillators with different frequencies.

1. It is often used as a clock oscillation circuit in microprocessor chips

In the most familiar single-chip microcomputer circuits, 6MHZ, 11.0592MHZ, 12MHZ and other crystal oscillator circuits are often used. For example, when this crystal oscillator is used with a microprocessor chip, the oscillator inside the chip and the two pins of the crystal oscillator are used. Docking will generate a clock signal consistent with the crystal identified by the crystal. The signals of these frequencies can coordinate the work of various parts inside the chip after frequency division.

We will find that some single-chip microcomputer chips will use a crystal oscillator with decimals, such as a 11.0592MHZ crystal oscillator, which is mainly set to facilitate the calculation of the baud rate when the single-chip microcomputer is communicating, so setting 11.0592MHZ is easy to reduce Communication error, improve the accuracy of communication. For example, if we use 115200 baud rate for communication, when we use 11.0592MH, we will get an integer of 96. If we use a 12MHZ crystal oscillator, we will get a decimal such as 10.41, which will bring a lot of errors. This is why there are The reason why the crystal frequency is not an integer.

Second, the crystal oscillator used in the computer motherboard

For example, there are various functional circuits in the computer motherboard, such as real-time clock circuit, audio circuit, network circuit, system clock circuit, etc., in these circuits, various crystal oscillators are needed. For example, the real-time clock circuit needs to use 32.768KHZ crystal oscillator, Audio circuit needs 24.5MHZ crystal oscillator, network circuit needs 25MHZ crystal oscillator, system clock circuit needs 14.318MHZ, etc. Some of these crystal oscillators are integers and some are decimals. The purpose of this is mainly to obtain the required oscillation period by frequency division according to the needs of the circuit, and further obtain the precise time. We can compare the crystal oscillator to the metronome used when playing the piano. Only with the coordination of the metronome can we play beautiful songs better. Then the crystal oscillator and the chip are combined to provide different clock frequencies for the entire system by frequency division.

  

3. Application in other electronic products

Crystal oscillators are used in many other electronic products, especially communication electronic products, such as walkie-talkie circuits, color TV circuit boards, electronic watches, DVD player circuits, etc. It can be said that as long as there is a need for a clock circuit, the crystal oscillator is essential. Fewer crystal resonators.

4. Crystal oscillator circuit

The crystal oscillator is a component that provides a frequency reference for the circuit. It is usually divided into two categories: active crystal oscillator and passive crystal oscillator. Passive crystal oscillator requires an oscillator inside the chip, and the signal voltage of the crystal oscillator is determined according to the starting circuit, allowing different crystal oscillators. voltage, but passive crystal oscillators usually have poor signal quality and accuracy, and need to accurately match the peripheral circuits (inductance, capacitance, resistance, etc.), if the crystal oscillator needs to be replaced, the peripheral circuits should be replaced at the same time. The active crystal oscillator does not need the internal oscillator of the chip, can provide a high-precision frequency reference, and the signal quality is better than that of the passive crystal oscillator.

Due to factors such as price, most circuits are designed with passive crystal oscillators in practical applications, unless the circuit design timing is extremely sensitive or there is no oscillator inside the chip (such as in some models of DSP or precision instruments).

The learning board adopts passive crystal oscillator. The following is the principle diagram of the learning board crystal oscillator.

  

XAL1 is a two-pin passive crystal oscillator, 11.0592MHZ oscillation frequency, matching capacitors are two 30P ceramic capacitors.

The manual of each chip will provide the standard circuit of the external crystal input, which will indicate the chip’s maximum usable frequency and other parameters, which should be mastered when designing the circuit. Different from the computer CPU, the crystal frequency that the single-chip microcomputer can receive is relatively low, but it is sufficient for general control circuits.

Another point is that some beginners may feel strange about the frequency of the crystal oscillator. Crystal oscillators such as 12M and 24M are better understood. Choosing a crystal oscillator such as 11.0592MHZ gives people a strange feeling. This problem is more troublesome to explain. Scholars will understand this when they practice serial port programming. This crystal oscillator is mainly used to design the baud rate of serial port or other asynchronous communication conveniently and accurately.

The above is the relevant content of “crystal oscillator” brought by this editor. Through this article, I hope that everyone has a certain understanding of the application of crystal oscillators with different frequencies, and has some understanding of the crystal oscillator circuit. If you like this article, you may wish to continue to pay attention to our website. The editor will bring more exciting content later. Finally, thank you very much for reading, have a nice day!

The Links:   G121XCE-L02 NL8060BC16-01