82562EZ_08 Datasheet, PDF (16/66 Pages) Intel Corporation – Dual Footprint

82562EZ(EX)/82547GI(EI) Dual Footprint Design Guide
.Table 6 lists the approved crystals for use with the 83547GI(EI) B1 steppings.
Table 6. 82547GI(EI) Recommended Crystals
Manufacturer
Raltron (<20 Ω ESR and +/-30 ppm)
TXC
Manufacturer's Part Number
AS-25.000-20-F-SMD-TR
6C25000355
3.1.1.1 Vibration Mode
Crystals in the frequency range listed in Table 5 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.
3.1.1.2 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.
3.1.1.3 Frequency Tolerance
The frequency tolerance for an Ethernet physical layer device 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.
Note: Intel recommends a frequency tolerance of ±30 ppm.
3.1.1.4 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). Several optional temperature ranges are currently
available, including -40° C to +85° C for industrial environments. Some vendors separate operating
temperatures from temperature stability. Manufacturers may also list temperature stability as 50
ppm in their data sheets.
Note: 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.
3.1.1.5 Calibration Mode
The terms “series-resonant” and “parallel-resonant” are often used to describe crystal circuits.
Specifying parallel mode is critical to determining how the crystal frequency is calibrated at the
factory.
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