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5.0
Crystal Selection Parameters
All crystals used with Intel® Ethernet controllers are described as "AT-cut," which refers to the
angle at which the unit is sliced with respect to the long axis of the quartz stone. The following
table lists crystals which have been used successfully in past designs (however no particular
product is recommended):
Table 8. Crystal Manufacturers and Part Numbers
Manufacturer
RALTRON
TXC CORPORATION - USA
Table 9
lists the crystal electrical parameters and provides suggested values for typical designs.
Designers should refer to criteria outlined in the 82563EB/82564EB Datasheet. The parameters are
described in the subsections following the table.
Table 9. Crystal Parameters
Parameter
Vibrational Mode
Nominal Frequency
Frequency Tolerance
Temperature Tolerance
Calibration Mode
Load Capacitance
Shunt Capacitance
Equivalent Series Resistance
Drive Level
Aging
5.1
Vibrational Mode
Crystals in the above-referenced frequency range are available in both fundamental and third
overtone. Unless there is a special need for third overtone, use fundamental mode crystals.
At any given operating frequency, third overtone crystals are thicker and more rugged than
fundamental mode crystals. Third overtone crystals are more suitable for use in military or harsh
industrial environments. Third overtone crystals require a trap circuit (extra capacitor and inductor)
in the load circuitry to suppress fundamental mode oscillation as the circuit powers up. Selecting
values for these components is beyond the scope of this document.
82563EB/82564EB LAN on Motherboard Design Guide
Part No.
AS-25.000-20-SMD-TR-NS7
6C25000131
Suggested Value
Fundamental
25.000 MHz
• ±30 ppm recommended
• ±50 ppm across the entire operating
temperature range (required by IEEE
specifications)
±30 ppm
Parallel
27 pF
6 pF maximum
50 Ω maximum
750 µW
±5 ppm per year maximum
Conditions
at 25° C
at 25° C
at 0° C to 70° C
at 25 MHz
17
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