MHz~MHz. 30Max. Fundamental/AT. MHz~MHz. 60Max. Third. Overtone /AT. Mechanical characteristics. Resistance to shock. that may be provided in Freescale Semiconductor data sheets and/or specifications can and do vary in different applications and actual performance may vary. series and range associated to this part. 49USMX Series. Technical Datasheet: MHZ 49USMX/30/50/40/18PF/ATF Datasheet. See all Technical Docs.
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A varactora diode with capacitance depending on applied voltage, is often used in voltage-controlled crystal oscillators, VCXO. The limitations in short-term stability are due mainly to noise from electronic components in the oscillator circuits.
A major reason xatasheet the wide use of crystal oscillators is their high Q factor. Other influencing factors are the overtone used, the mounting and electrodes, impurities in the crystal, mechanical strain, crystal geometry, rate of temperature change, thermal history due to hysteresisionizing radiation, and drive level. Series resistance of swept crystals is unaffected. A special cut, a double-rotated cut with improved characteristics for oven-stabilized oscillators.
Other dynamic stress inducing factors are shocks, vibrations, and acoustic noise. Retrieved 26 April Quartz crystals are manufactured for frequencies from a few tens of kilohertz to hundreds of megahertz. Atmospheric pressure changes can also introduce deformations to the housing, influencing the frequency by changing stray capacitances.
The two differ in their optical rotation but they are identical in other physical properties.
Crystal oscillator – Wikipedia
The effects of acceleration and vibration tend to dominate the other noise sources; surface acoustic wave devices tend to be more sensitive than bulk acoustic wave BAW ones, and the stress-compensated cuts are even less sensitive.
The mobility of interstitial ions depends strongly on temperature. Plastic housings can be used as well, but those are not hermetic and dataeheet secondary sealing has to be built around the crystal.
Crystal Parameters Parametercharacteris tics of the piezoelectric crystal and the on-chip crystal oscillator circuitry designed into 1.6000circumventing oscillator start-up problems.
The oscillator circuits 2 Crystal frequency tolerance Aug.
The crystals are usually mounted in hermetically sealed glass or metal cases, filled with a dry and inert atmosphere, usually vacuum, nitrogen, or helium. Low drive levels are xatasheet for higher stability and lower power consumption of the oscillator.
This modulates the resonant frequency to a small degree by the frequency of the vibrations. High-intensity radiation can stop the oscillator by inducing photoconductivity in the crystal and transistors; with a swept crystal and properly designed circuit the oscillations can restart within 15 microseconds after the radiation burst.
Crystals undergo slow gradual change of frequency with time, known as aging. The crystals have to be driven at the appropriate drive level.
The reverse process however is not entirely homogeneous and crystal twinning occurs. Crystaloscillator is designed to work with an external piezoelectric Quartz exists in several phases.
But, like many other mechanical resonators, crystals exhibit several modes of oscillation, usually at approximately odd integer multiples of the fundamental frequency. Sweeping can also be used to introduce one kind of an impurity into the crystal.
The overtone modes are at frequencies which are approximate, but not exact odd integer multiples of that of the fundamental mode, and overtone frequencies are therefore not exact harmonics of the fundamental. The oven-controlled OCXOs require usually 3—10 minutes for heating up to reach thermal equilibrium; the oven-less oscillators stabilize in several seconds as the few milliwatts dissipated in the crystal cause a small but noticeable level of internal heating.
Crystals suffer from minor short-term frequency fluctuations as well. While AT cuts tend to be fairly forgiving, with only their electrical parameters, stability and aging characteristics being degraded when overdriven, low-frequency crystals, especially flexural-mode ones, may fracture at too high drive levels.
Strip resonators, usually AT cuts, are smaller and therefore less sensitive to mechanical shocks. Although crystal oscillators still most commonly use quartz crystals, devices using other materials are becoming more common, such as ceramic resonators.
Sensitive to air damping, to obtain optimum Q it has to be packaged in vacuum. Gold also does not form oxides; it adsorbs organic contaminants from the air, but these are easy to remove. A DC voltage bias between the electrodes can accelerate the initial aging, probably by induced diffusion of impurities through the crystal. Capacitor types Ceramic resonator Crystal oscillator Inductor Parametron Relay reed relay mercury switch. Inclusions of water may be present in fast-grown crystals; interstitial water molecules are abundant near the crystal seed.
Its second overtone is about six times the fundamental frequency.
Ionization produces electron-hole pairs; the holes are trapped in the lattice near the Al atom, the resulting Li and Na atoms are loosely trapped along the Z axis; the change of the lattice near the Al atom and the corresponding elastic constant then causes a corresponding change in frequency.
For this reason, atomic oscillators are used for applications requiring better long-term stability and accuracy. Even if the series resistances at the spurious resonances appear higher than the one at wanted frequency a rapid change in the main mode series resistance can occur at specific temperatures when the two frequencies are coincidental.
This property is known as electrostriction or inverse piezoelectricity. Operates at the same frequencies as the AT cut. Barkhausen stability criterion Harmonic oscillator Leeson’s equation Nyquist stability criterion Oscillator kxs noise Phase noise. The chief application is the Patent 3,Issue date: