Crystal Oscillator Series II--Types and packages of crystal oscillator

The electronic components containing quartz resonant crystals can be divided into two main categories:
　　quartz crystals (crystal or xtal) are quartz wafers plus electrodes and housings . Also known as quartz oscillator or quartz crystal resonator (Crystal resonator). This is a simple quartz crystal passive element, does not contain the active element , need to match the external circuit to produce oscillation . This is a passive (non-active) element, also known in the mainland as passive crystal (meaning: Passive quartz crystal oscillator). Quartz crystals are usually two pin-connected electronic components.

Internal structure after removal of the general crystal oscillator (Crystal Core)

internal structure of tuning fork crystal for low frequency crystal oscillator design

　　quartz crystal oscillator (Crystal oscillator, abbreviated OSC or XO) is a module containing quartz crystals and oscillating circuits , which requires a power supply that generates an oscillating signal output directly. The whole module is also an active element because of its active component, and it has the active crystal in the mainland. Quartz oscillator is usually a four-pin electronic components, two of which are power supply, one for the oscillation signal output, the other for the empty foot or control.

Internal structure of active crystal oscillator

With the development of communication and digital technology, the frequency stability and the requirement of temperature adaptability are different in the actual product design, in order to improve the parameter level of crystal oscillator, different types of active crystal are developed.
Quartz crystal oscillator modules are more common in the following categories:
XO: General type (Crystal oscillator)
TCXO : Temperature compensated type (temperature compensated crystal oscillator)
OCXO : thermostatic type (oven-controlled crystal oscillator)
VCXO : Voltage-controlled (voltage-controlled crystal oscillator)

The current crystal vibration of several packaging formats:
A Passive Crystal oscillator:

Active Crystal Package form:

1, ordinary active crystal XO

2, TCXO: Temperature compensation type (temperature compensated crystal oscillator) The appearance of some and common active crystal, but the internal chip has a temperature compensation algorithm

3, VCXO voltage control type (voltage-controlled crystal oscillator) Basic Package size and tcxo the same
4, OCXO: Constant temperature (oven-controlled crystal oscillator), the reason is called constant temperature crystal is mainly to prevent the internal crystal and circuit too much affected by the temperature and the accuracy of the change, through the semiconductor material to produce a constant temperature environment, To produce a stable clock frequency.

The main frequency points of several crystal oscillators are described below:
32.768kHz = 215, easy crossover to 1Hz, widely used in quartz clocks, real-time clock in the product
3.58MHz (only decimal two bits) the American Standard analogy color TV system (NTSC) color subcarrier frequency, because of the use of color television and large-volume production, so easy to obtain and cheap, is also widely used in many other devices, such as dual-tone multi-frequency telephones and so on
4MHZ Common integer Frequency
8MHz
10MHz for standard frequency
11.0592MHz = 115,200x96 = 1.8432mhzx6 for accurate UART generation (Universal Asynchronous Receiver/transmitter Universal Asynchronous transceiver, commonly used in mobile phones), Commonly referred to as the UART operating frequency, and is exactly the original 8051 microcontroller operating frequency limit
12MHz
14.318MHz (three bits only) four times times the color subcarrier frequency of the US NTSC color TV, which was used early because it is easy to produce color TV signals and can be used for other parts, such as Apple II and the original IBM PC, which are widely adopted for easy access.
16MHz
20MHz

22.1184MHz

Crystal Oscillator Series II--Types and packages of crystal oscillator