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Oscilent quartz crystal

Quartz crystals are manufactured according to industry standard guidelines pertaining to such variables as package type, (a.) Mode of Operation, (b.) Equivalent Series Resistance, (c.) Shunt Capacitance, and (d.) Drive Level. Although these parameters may vary slightly between manufactures, and review of these parameters should be done when crossing between manufacturers, one can generally assume that these parameters will remain constant.

a. Mode of Operation (Resonance Frequency):
A Quartz Crystal has two basic modes of operation comprising Fundamental and Overtone Modes. For frequencies below 30MHz, a crystal manufacturer will use the Fundamental Mode of operation. For frequencies exceeding 30 MHz, overtone modes are recommended (overtones are not precise integer multiples of the fundamental as in a similar concept found in harmonics) Higher Fundamental mode Crystals are possible, however the crossover at 30MHz is generally considered the point where the Fundamental mode Crystal becomes more expensive to produce due to thinning of the quartz blank (increasing breakage during production). Using Overtone Modes in production therefore reduces manufacturing costs for higher frequency applications. A good rule of thumb is to assume the a Crystal manufacturer will produce a Fundamental Crystal below 30MHz, and an Overtone Crystal above 30MHz. If higher frequencies are required in the Fundamental Mode, please contact Oscilent for support and details on Inverted Mesa technology.

b. Equivalent Series Resistance (ESR):
The Equivalent Series Resistance is the resistive element of the quartz crystal equivalent circuit. This range is normally found to be 25-100 ohms for most Quartz Crystals and is usually specified as a maximum value. Typically, these values are specified according to frequency ranges and are very similar across multiple manufactures because similar holder types, electrodes, modes of operation, and mounting structures are used in achieving specific frequencies. More significant at lower frequencies, it should be noted that ESR values at a given frequency for an AT- strip cut crystal (commonly used in Surface Mount devices) are higher than that of the standard (round blank) design (commonly found in Through Hole devices)

c. Shunt Capacitance:
The electrodes present in a Quartz Crystal, plus the stray capacitance of the holder, form a capacitance in parallel with the LC model. Generally, the Shunt Capacitance is sought to be as low as possible in manufacturing the device, as some oscillators cannot tolerate an excessive value. Because Shunt Capacitance may vary according to the size of the Crystal, manufacturers will normally designate a maximum value usually at 7.0pF. If a lower value is required, we suggest contacting Oscilent Engineering Support.

d. Drive Level:
Specified by Quartz Crystal manufacturers to provide a guideline for maximum values, the Drive Level should be held to a minimum to avoid problems with Aging, Stability, nonlinear coupled modes, and other nonlinear effects. Improvements in phase noise performance can be realized with increased drive levels, however, so careful consideration should be given to this Electrical Parameter when approaching the maximum suggested level.

Variables that must be selected by the design engineer
Variable Electrical parameters are those that the Design Engineer must specify when selecting a Quartz Crystal device for any particular application. Although Oscilent offers a wide range of these variables in the Part Number Guide section of our Specification, other, more custom parameters, are available:

a. Package Type: Will the package be Through Hole or Surface Mount, and are there size constraints with either.

b. Frequency

c. Load Capacitance: The specified Load Capacitance is dependent on the Resonance Mode required in the application ( for more detailed information on this subject Definitions of Load Capacitance ) For Series resonance, no Load Capacitance is required ("SR" in the Oscilent part number). For Parallel Resonance, the Load Capacitance specified by the Design Engineer will be used to calibrate the Quartz Crystal thereby effecting the major operating characteristics of the device, including initial Frequency Tolerance.

d. Frequency Tolerance: At 25 degree Celsius, an amount of initial frequency deviation acceptable for the application is required. Tighter specifications of Frequency Tolerance lower yield in Quartz Crystal Blank production thereby serving to increase production costs.

e. Stability: Over the Operating Temperature Range, an amount of total deviation acceptable for the application. Tighter specifications of Stability lower yield in Quartz Crystal Blank production thereby serving to increase production costs.

f. Operating Temperature: Standard Operating Temperature ranges are generally considered as -20-+70 degrees Celsius (considered "commercial" Operating Temperature), and -40-+85 degrees Celsius (considered "Industrial" Operating Temperature) Other Operating temperature ranges are available and should be specified and/or discussed with an Oscilent Technical advisor.

Manufacturer/supplier's information

Company name:		Oscilent Corportation [ Homepage ]
Business address:		18195 East McDurmott Street Building D Irvine . CA USA
Zip/postal code:		92614
Telephone number:		1.949.252.0522
Fax number:		1.949.252.0599
Contact name:		Sales [ Email ]

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Product groups: quartz crystal

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