MCU, Chinese: Microcontroller Unit, English full name: Microcontroller Unit (abbreviation: MCU).
MCU, also known as Single Chip Microcomputer or Single Chip Microcomputer, appropriately reduces the frequency and specifications of the Central Processing Unit (CPU), and combines memory, counter (Timer), USB, A /D conversion, UART, PLC, DMA and other peripheral interfaces, and even LCD drive circuits are integrated on a single chip to form a chip-level computer that can perform different combinations of control for different applications, such as network communications, industrial automation, and intelligent medical equipment. Wait, you can see the MCU.
MCU is equivalent to the human brain. Only with MCU can electronic devices carry out memory, calculation, and processing.
MCU is the human brain, then the crystal oscillator is the human heart.
The crystal oscillator is an electronic component that generates the clock frequency required by the MCU. The higher the clock frequency provided by the crystal oscillator, the faster the microcontroller will run.
The execution of all instructions received by the MCU is based on the clock frequency provided by its crystal oscillator. The reason why the crystal oscillator is likened to the heart of a digital circuit is because all the work of a digital circuit is inseparable from the clock signal. Without the crystal oscillator in the MCU, there is no clock cycle. Without the clock cycle, no program code can be executed.
Crystal oscillators are divided into crystal resonators (XTAL) and crystal oscillators (XO).
Crystal resonator, in English is Crystal Units, referred to as crystal (some people also call it passive crystal oscillator). Currently, the most widely used in the market is crystal oscillator based on quartz wafer. 32.768kHz crystal resonator. Including patch tuning fork crystal oscillator, cylindrical and DIP type. AT crystal resonator adopts AT cutting method, and the frequency range based on fundamental wave covers 4MHz~64MHz. Various specifications and sizes are available. SAW resonator is used for high frequency from 300MHz to 870MHz, ultra-thin and ultra-small size, and can be used in In areas such as car door locks and near field communications, dedicated low-power wireless communications.
The crystal oscillator has a built-in quartz crystal resonator and supporting circuits, which eliminates the troublesome matching and debugging of the oscillator circuit, has good signal quality, and the connection method is relatively simple. Quartz crystal oscillators are better than crystal resonators in terms of stability, and their accuracy is also more advantageous than crystal resonators. High stability is maintained throughout the entire operating temperature range, and the performance of crystal oscillator types such as high-frequency differential crystal oscillators and temperature-compensated crystal oscillators is even more obvious. If the product has higher requirements for accuracy and temperature stability, it is recommended to choose a crystal oscillator.
The common pin connection method of a four-pin active crystal oscillator: one pin is floating, two pins are connected to ground, three pins are connected to the output, and four pins are connected to the voltage. 6-pin and 10-pin crystal oscillators are mostly used in fields such as temperature-compensated crystal oscillators or differential crystal oscillators.
There are also domestic brands for MCU, such as GD GigaDevice, Zhongying, Hangshun, Xianji, Lingdong Micro, etc. Whether these brands selected a certain brand of crystal oscillator when doing original design remains to be further confirmed.
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"Chip + crystal oscillator" is the future development direction.
Have you ever encountered such trouble in crystal circuits?
1. The crystal circuit is designed according to IC recommendations, but there is a large deviation in frequency, or the entire crystal circuit cannot work.
2. During mass production, it was discovered that there was a problem with the crystal circuit. Either the frequency was wrong or it could not vibrate. You ask the supplier and they say: There is nothing wrong with the crystal itself.
In fact, many of the above are caused by the lack of good matching at the beginning of the crystal circuit design. This is a very time-consuming design, but you don’t have to worry now. We have always provided such services to help customers with loop matching of passive crystals and help you adjust frequency, drive power and oscillation capability. The original manufacturer must solve these problems during the design stage.
We can evaluate your crystal circuit on your PCB board and recommend suitable values, (e.g., Cg, Cd, Rf, Rd)
You only need to provide the following information:
1. Circuit boards that can work continuously
2. Schematic diagram and PCB diagram of the crystal part
3. Power supply method
4. Currently used crystal information
Staff are conducting CE testing, as above
Standard crystal circuit schematic diagram
RD-current limiting resistor丨Rf-reverse resistor丨X-quartz crystal
CG-frequency adjustment capacitor, gate terminal丨CD-frequency adjustment capacitor, drain terminal
Epson Shanghai Laboratory
What our standard tests include
Proposal format (example)
Advantages of EPSON CE testing
*Epson will recommend the most suitable circuit matching and the most suitable crystal to help you solve problems such as insufficient crystal circuit accuracy and no vibration.
*Our CE test is more reasonable and efficient, because what we recommend is not only the frequency adjustment, but also the driving power and circuit oscillation ability.
*Epson's service is completely free, which saves you time and design costs.
Precautions for using in-line crystals are as follows: