Ordinary crystal oscillators can be roughly divided into ceramic crystal oscillators and quartz crystal oscillators. There are also some special crystal oscillators. Such as constant temperature crystal oscillator, temperature compensated crystal oscillator 　　The crystal oscillator is an oscillator that uses a quartz crystal. Its accuracy is very high, and it can generate a very stable frequency, and its thermal stability is better than that of a discrete component oscillator. From the point of view of function, it can be said that the crystal oscillator is the "heartbeat" generator of each board. If the "heartbeat" of a person is disordered, it will be sick. Similarly, if the "heartbeat" of the computer board is disordered, various strange faults will also occur

Recently, I found that the clock displayed on the computer is always slowing down inexplicably. After every time I re-adjusted it, it slowed for several minutes after a month or two. Although it was a minor problem, it also brought me some trouble, such as a timer switch. machine. It seems we have to deal with this problem. 　　Generally, there is a button battery on the motherboard to maintain the information stored in the CMOS after the host is powered off. The power required for the clock in the computer is also supplied by this battery. If the computer clock slows down, generally speaking, the CMOS battery fails. caused. Therefore, I went to the Computer City and spent five yuan to buy a button battery for the motherboard, and then opened the case. Good guy, because there has been no dust removal for a long time, a thick layer of dust has fallen on the motherboard. Leave it alone, find the CMOS battery, remove it, replace it with the newly purchased battery, turn it on, and use a more accurate electronic watch to do a comparison test, and find that the time in the computer is still slow. What's wrong? It seems that the battery is not the primary problem

Crystal oscillators can be divided into two categories, quartz crystal oscillators and ceramic crystal oscillators, from the material, and subordinate crystal oscillators can be divided into passive crystal oscillators and active crystal oscillators. Quartz crystals and ceramic crystals are very conducive to distinguishing from the appearance, after all, they are two completely different materials. The passive crystal oscillator and the active crystal oscillator are sometimes silly and unclear. Especially for 2520 SMD crystals, 3225 SMD crystals, 5032 SMD crystals and four-pin packaged quartz crystals, there are both passive crystals and active crystals. From the appearance alone, we are very distinguish. So today, Ruitai Electronics has carefully sorted out how to correctly identify passive crystal oscillators and active crystal oscillators. 　　Passive crystal oscillators are also called resonators. The pins of crystal oscillators are usually pin 2 and pin 4. Passive crystal oscillators need to use an external circuit to vibrate in the circuit, and they cannot be vibrated by themselves. Passive crystal oscillators have plug-in shapes and patch shapes, such as the 32.768KHZ cylindrical crystals we often see, or 49/S crystal packaging, 49/U crystal packaging, ceramic two-pin, three-pin plug-in packaging; The more common chip crystal oscillators are the 3215 chip crystal oscillator package series

Each single-chip microcomputer system has a crystal oscillator. The whole process is called a crystal oscillator. The crystal oscillator plays a very important role in the single-chip microcomputer system. It combines the internal circuit of the single-chip microcomputer to generate the necessary clock frequency of the single-chip microcomputer. The execution of all the instructions of the single-chip microcomputer is established. On this basis, the higher the clock frequency provided by the crystal oscillator, the faster the operating speed of the microcontroller. 　　The crystal oscillator uses a crystal that can convert electrical and mechanical energy into each other to work in a resonant state to provide stable and precise single-frequency oscillation. Under normal working conditions, the absolute accuracy of ordinary crystal oscillator frequencies can reach 50 parts per million. Advanced accuracy is higher. Some crystal oscillators can also adjust the frequency within a certain range by an external voltage, which is called a voltage-controlled oscillator (VCO)

Crystal oscillators are also called active crystal oscillators. The other type is called crystal resonators (passive crystal oscillators). Both are generally referred to as crystal oscillators. In the purchase of crystal oscillators, there are some differences between the purchase requirements of active and passive crystal oscillators. Today, I will talk about the purchase precautions of the 5-point crystal oscillator provided. 　　1. The working principle of crystal oscillator 　　The crystal oscillator can generate the clock frequency signal necessary for the central processing unit (CPU) to execute instructions. All instructions of the CPU are executed on this basis. The higher the frequency of the clock signal, the faster the CPU generally runs. As long as it is an electronic product that contains a CPU, it contains at least one clock source. Even if the actual oscillator circuit is not visible outside, it is integrated inside the chip. It is called the heart of the circuit system