82583V Datasheet, PDF (331/374 Pages) Intel Corporation – Intel® 82583V GbE Controller

Design Considerations—82583V GbE Controller
• Use 27 pF (5% tolerance) 0402 load capacitors.
• Place load capacitor solder pad directly in line with circuit trace (see Figure 51,
point A).
• Use 50 Ω impedance single-ended microstrip traces for the crystal circuit.
• Route traces so that electro-magnetic fields from XTAL2 do not couple onto XTAL1.
No differential traces.
• Route XTAL1 and XTAL2 traces to nearest inside corners of crystal pad (see
Figure 51, point B).
• Ensure that the traces from XTAL1 and XTAL2 are symmetrically routed and that
their lengths are matched.
• The total trace length of XTAL1 or XTAL2 should be less than 750 mils.
Crystal Pad
Crystal
“B”
“B”
Capacitor
27pF
0402
“A”
Less than 660 mils
Capacitor
27pF
0402
Crystal Pad
Xtal2 Xtal1
Ethernet Controller
Figure 51. Recommended Crystal Placement and Layout
11.4
Oscillator Support
The 82583V clock input circuit is optimized for use with an external crystal. However,
an oscillator can also be used in place of the crystal with the proper design
considerations (see Table 19 for detailed clock oscillator specifications):
• The clock oscillator has an internal voltage regulator of 1.9 V dc to isolate it from
the external noise of other circuits to minimize jitter. If an external clock is used,
this imposes a maximum input clock amplitude of 1.9 V dc. For example, if a
3.3 V dc oscillator is used, it's signal should be attenuated to a maximum of
1.9 V dc with a resistive divider circuit.
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