82583V Datasheet, PDF (327/374 Pages) Intel Corporation – Intel® 82583V GbE Controller

Design Considerations—82583V GbE Controller
11.3
11.3.1
Table 56.
11.3.1.1
11.3.1.2
11.3.1.3
11.3.1.4
Note:
Crystal Support
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.
Table 56 lists crystals which have been used successfully in other designs (however, no
particular product is recommended):
Crystal Manufacturers and Part Numbers
Manufacturer
KDS America
NDK America Inc.
TXC Corporation - USA
Part No.
DSX321G
41CD25.0F1303018
7A25000165
9C25000008
For information about crystal selection parameters, see section 11.7 and Table 18.
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.
Nominal Frequency
Intel Ethernet controllers use a crystal frequency of 25.000 MHz. The 25 MHz input is
used to generate a 125 MHz transmit clock for 100BASE-TX and 1000BASE-TX
operation – 10 MHz and 20 MHz transmit clocks, for 10BASE-T operation.
Frequency Tolerance
The frequency tolerance for an Ethernet Platform LAN Connect is dictated by the IEEE
802.3 specification as ±50 parts per million (ppm). This measurement is referenced to
a standard temperature of 25° C. Intel recommends a frequency tolerance of ±30 ppm.
Temperature Stability and Environmental Requirements
Temperature stability is a standard measure of how the oscillation frequency varies
over the full operational temperature range (and beyond). Some vendors separate
operating temperatures from temperature stability. Manufacturers may also list
temperature stability as 50 ppm in their data sheets.
Crystals also carry other specifications for storage temperature, shock resistance, and
reflow solder conditions. Crystal vendors should be consulted early in the design cycle
to discuss the application and its environmental requirements.
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