Key Parameters Needed to Specify a Crystal
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This parameter is valid for crystals used in load or parallel resonant oscillator circuits. Cload is the capacitance value, specified in pf, used during frequency calibration. e.g. 18 pf
ESR (Equivalent Series Resistance):
This resistance represents the equivalent impedance of the crystal at its resonant frequency and is specified in Ohms. e.g. 50 ohms max
Crystals have sharp resonant peaks at their fundamental frequency and at odd harmonics above the fundamental. Crystals designed to function at one of these harmonics are called overtone crystals. At higher oscillator frequencies overtone designs reduce cost by using thicker, and easier to manufacture, crystal elements. The majority of crystals in use today are fundamental or third overtone. e.g. Fund
This is the maximum deviation from nominal frequency at 25° C. Calibration tolerance is specified in Parts-Per-Million (ppm). e.g. ±30ppm
Stability is the maximum deviation of the crystal frequency over the specified operational temperature range referenced to 25° C. Like calibration tolerance, stability is specified in ppm. The combined effects of calibration tolerance and stability are additive over the operational temperature range. E.g. ±50ppm
Part Number Builder:
A complete guide to building a crystal part number can be found in the crystal product section at www.pletronics.com.
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