The clock source is used to provide a square wave clock pulse signal with stable frequency and level matching for the ring pulse generator.It is usually composed of a quartz crystal oscillator and a positive feedback oscillation circuit composed of NAND gate, and its output is sent to the ring pulse generator.
The clock source is used to provide a square wave clock pulse signal with stable frequency and level matching for the ring pulse generator.It is usually composed of a quartz crystal oscillator and a positive feedback oscillation circuit composed of NAND gate, and its output is sent to the ring pulse generator.
crystal oscillator
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Crystal oscillator refers to cutting a slice (referred to as wafer for short) from a quartz crystal at a certain azimuth,Quartz crystal resonator, referred to as quartz crystal or crystal, crystal oscillator [1];The IC is added inside the package to form the crystal of the oscillation circuitelementIt is called crystal oscillator.Its products are generally packaged with metal shells, but also with glass shells, ceramics or plastics.
working principle
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Quartz crystal oscillator is an oscillator with high accuracy and stability, which is widely used in various kinds of oscillation circuits such as color TV, computer, remote controller, etc., as well as in communication systems for frequency generators, generating clock signals for data processing equipment and providing reference signals for specific systems [1].
Quartz crystal oscillator is a kind of resonant device made of piezoelectric effect of quartz crystal (crystal of silicon dioxide). Its basic composition is roughly as follows: cut a thin slice (referred to as wafer for short, which can be square, rectangular or circular) from a quartz crystal at a certain azimuth angle, and coat silver layers on its two corresponding surfaces as electrodes,A lead wire is welded on each electrode and connected to the pin, and then the package shell is added to form a quartz crystal resonator, which is called quartz crystal or crystal, crystal oscillator for short.Its products are generally packaged with metal shells, but also with glass shells, ceramics or plastics [1].
If an electric field is applied to two electrodes of the quartz crystal, the chip will produce mechanical deformation.On the contrary, if mechanical pressure is applied on both sides of the wafer, an electric field will be generated in the corresponding direction of the wafer. This physical phenomenon is called piezoelectric effect.If an alternating voltage is applied to the two poles of the chip, the chip will generate mechanical vibration, and at the same time, the mechanical vibration of the chip will generate an alternating electric field.In general, the amplitude of the mechanical vibration of the wafer and the amplitude of the alternating electric field are very small. However, when the frequency of the applied alternating voltage is a certain value, the amplitude increases significantly, which is much larger than the amplitude at other frequencies. This phenomenon is called piezoelectric resonance, which is very similar to the resonance phenomenon of the LC circuit.Its resonant frequency is related to the cutting mode, geometric shape and size of the chip [1].
When the crystal does not vibrate, it can be regarded as a flat plate capacitor called electrostatic capacitance C. Its size is related to the geometric size of the chip and the electrode area, which is generally about several to dozens of PF.When the crystal oscillates, the inertia of mechanical vibration can be equivalent to the inductance L.Generally, the value of L ranges from tens of mH to hundreds of mH.The elasticity of the chip can be equivalent to the capacitance C. The value of C is very small, generally only 0.0002~0.1pF.The loss caused by friction during wafer vibration is equivalent to R, which is about 100 Ω.Since the equivalent inductance of the chip is large, C is small, and R is small, the quality factor Q of the circuit is large, up to 1000~10000.In addition, the resonant frequency of the chip itself is basically related to the cutting mode, geometric shape and size of the chip, and can be done accurately. Therefore, the oscillation circuit composed of quartz resonator can achieve high frequency stability.
