82541PI(ER) and 82562GZ(GX) Dual Footprint LOM Design Guide
Application Note (AP-468)
7
3.0
Ethernet Component Design Guidelines
This section provides recommendations for selecting components and connecting special pins. The
main design elements are the 82562GZ(GX) PLC device or the 82541PI(ER) Gagabit Ethernet
controller, external resistor connections (82562GZ(GX) only), a magnetics module with RJ-45
connector, and a crystal clock source.
3.1
General Design Considerations for Ethernet Controllers
These recommendations apply to all designs, 10/100 Mbps or 10/100/1000 Mbps.
Good engineering practices should be followed with respect to unused inputs by terminating them
with pull-up or pull-down resistors, unless the datasheet, design guide or reference schematic
indicates otherwise. Do not attach pull-up or pull-down resistors to any balls identified as reserved
(unless explicitly included in the reference schematic). These devices may have special test modes
that could be entered inadvertently.
3.1.1
Crystal Selection Parameters
Quartz crystals are generally considered to be the mainstay of frequency control components due to
their low cost and ease of implementation. They are available from numerous vendors in many
package types and with various specification options.
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.
lists the crystal electrical parameters and provides suggested values for typical designs. The
parameters listed are described in the following subsections.
Table 5. Crystal Parameters
Parameter
Suggested Value
Vibration Mode
Fundamental
Nominal Frequency
25,000 MHz at 25
°
C (required)
Frequency Tolerance
•
±30 ppm recommended; ±50 ppm across the entire operating
temperature range as required by IEEE specifications
•
±30 ppm required for the 82562GZ(GX)
Temperature Stability
•
±50 ppm at 0
°
C to 70
°
C
•
±30 ppm at 0
°
C to 70
°
C required for the 82562GZ(GX)
Calibration Mode
Parallel
Non Operating Temperature
Range
-40 to 90
°
C for the 82562GZ(GX)
Load Capacitance
•
16 pF to 20 pF
•
20 pF required for the 82562GZ(GX)
Pullability from Nominal Load
Capacitance
15 ppm/pF maximum for the 82562GZ(GX)
Shunt Capacitance
6 pF maximum
Equivalent Series Resistance
50
Ω
maximum