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Crystal Oscillator
Some electronic equipment requires AC signals with highly stable frequency, but LC oscillators have poor stability and their frequency is prone to drift (that is, the frequency of the generated AC signal is prone to change). Using a special component – quartz crystal – in the oscillator can generate highly stable signals. This kind of oscillator using quartz crystal is called a crystal oscillator.
Crystal oscillators have the piezoelectric effect, that is, when an external voltage is applied to the two poles of the wafer, the crystal will deform; conversely, if an external force deforms the wafer, 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 fixed). Crystal oscillators use a crystal that can convert electrical energy and mechanical energy into each other, and work in a resonant state to provide stable and accurate single-frequency oscillation. Under normal operating conditions, the absolute frequency accuracy of ordinary crystal oscillators can reach fifty parts per million. Using this characteristic, crystal oscillators can provide relatively stable pulses and are widely used in the clock circuits of microchips. Most wafers are made of quartz semiconductor materials, and the shell is encapsulated in metal.
Main Application Fields and Frequency Points of Crystal Oscillators
I. Computer Peripheral Electronic Accessories
Motherboard: 14.318MHZ, 24.576MHZ, 25MHZ, 27MHZ, 32.768KHZ
Monitor: 8M/14.31818MHZ, 12.000MHZ, 24.000MHZ, 28.224MHZ
Hard Disk: 23.040MHz, 28.224MHz
Optical Drive: 33.8688MHz, 16.9344MHz, 18.432MHz
Keyboard: 6.000MHz
Mouse: 6.000MHz, 12.000MHz, 24.000MHz
Camera: 12.000MHz
Bluetooth: 16.000MHz
Wireless WIFI: 25.000MHz, 2.5G/3G (40.000MHz, 44.000MHz)
Network Transmission ADSL: 12.288MHz, 35.328MHz, 50.000MHz
Crystal oscillators on the motherboard are mainly divided into:
Crystal Oscillator – Connected Chip – Frequency – Clock: Crystal Oscillator Clock Chip, 14.318MHz
Real-Time Crystal Oscillator – South Bridge, 32.768KHz
KBC, 32.768KHz
Network Card Crystal Oscillator – Network Card Chip, 25.000MHz
Sound Card Crystal Oscillator – Sound Card Chip, 24.576MHz
Graphics Card Crystal Oscillator – Graphics Card Chip, 27MHz
Card Reader Crystal Oscillator – Card Reader Chip, 12MHz
The most important crystal oscillators on the motherboard are the real-time crystal oscillator and the clock crystal oscillator. The real-time crystal oscillator provides the oscillation frequency for the south bridge, and almost all frequencies on the motherboard are based on the clock crystal oscillator. If they are damaged, the motherboard cannot work normally.
Function of Crystal Oscillator: It forms an oscillation circuit with clock chips, sound card chips, network card chips, graphics cards and other chips, and is the most important clock signal source on the entire board.
II. Communication Applications
Fixed Telephone: 3.579545MHz
Cordless Telephone: 10.250MHz, 10.245MHz, 10.240MHz, 10.100MHz, 13.824MHz, 32.768KHz
PHS: 19.2MHz
Mobile Phone MTK Scheme TCXO: 27.000MHz, 24.000MHz, 26.000MHz
Wireless Bluetooth, GPS, RF (2.4G), Car Reverse Radar, Navigation: 16.000MHz, 12.000MHz, 26.000MHz
Walkie-Talkie: 21.400MHz, 21.7000MHz
III. Consumer Electronics
Television: 4.433619MHz, 3.579545MHz, 12.000MHz
DVD: 16.9344MHz, 27.000MHz
Power Amplifier: 4.500MHz, 7.200MHz, 12.288MHz
Audio: 4.500MHz, 7.200MHz
Set-Top Box: 27.000MHz, 13.500MHz, 54.000MHz
Remote Control: 455E, 4.000MHz, 32.768KHz
Air Conditioner: 4.194304MHz, 4.000MHz
Small Home Appliances (Kitchen, etc.): 4.000KHz, 6.000MHz, 4.19430MHz, 32.768KHz
Toy and Game Category (Remote Control)/Game Console: 6.000MHz, 27.145MHz, 27.125MHz, 49.860MHz, 12.000MHz, 24.000MHz, 10.000MHz, 8.000MHz, 48.000MHz
PMP, MP4: 27.000MHz, 12.000MHz, 24.576MHz
Camera, Video Camera: 27.000MHz, 54.000MHz, 36.000MHz
IV. Industrial Automation, Intelligence and Industrial Control
Bank Financial System/Encryption Dog/Tax Control System/Remote Meter Reading System/Testing Instrument/Ultrasound:
50.000MHz, 3.579545MHz, 48.000MHz, 4.000MHz, 12.000MHz, 50.000MHz, 10.000MHz, 8.000MHz, 6.000MHz
Security Category: 13.560MHz, 24.000MHz, 12.270MHz
Medical Instruments: Instruments and Meters, Micrometers, Calipers, Detection, etc.
Automotive Electronics: Oil Control System/Remote Control/GPS/Reverse Radar/Tire Pressure Testing/Car Audio, etc. It is also applied to access control systems, video phones/intercom doors, community intelligent control systems, health function products (blood pressure monitors, electronic scales, massagers, etc.)
Application of Active and Passive Crystal Oscillator Frequencies
Optical Transceiver:
25MHZ (passive: 49s, active: 7050), 65.536MHZ, 74.25MHZ, 80MHZ, 85MHZ, 100MHZ, 120MHZ, 125MHZ, 148.5MHZ, 150MHZ, 200MHZ
Audio Digital Effect Processor
12.288MHZ, 16.384MHZ, 8MHZ, 24MHZ
Security (Cameras, Alarms)
32.768KHZ, 24MHZ, 25MHZ, 27MHZ, 37.125MHZ, 45MHZ, 48MHZ, 50MHZ, 54MHZ, 74.25MHZ, 100MHZ, 108MHZ, 125MHZ
Bluetooth Headset
16MHZ, 26MHZ, 32.768KHZ
Automotive (Front and Rear Cameras – Navigation)
27MHZ, 19.2MHZ
Walkie-Talkie
19.2MHZ (temperature-compensated), 24MHZ, 26MHZ (temperature-compensated)
Clock
32.768KHZ
Embedded Design
7.3728MHZ, 12MHZ, 24MHZ, 24.576MHZ, 25MHZ, 27MHZ, 14.31818MHZ, 48MHZ, 32.768KHZ
Mobile Phone
32.768KHZ, 26MHZ