82551IT Datasheet, PDF (101/102 Pages) Intel Corporation – Fast Ethernet PCI Controller

Networking Silicon — 82551IT
LILED
ACTLED
SPEEDLED
A12
C11
B11
3VSB
2
1
1
2
LED
330
2
330
1
The 82551IT can drive three
LEDs with the cathode of
each device connected to
the 82551IT as shown with
the SPEEDLED or a two LED
configuration can be used,
as shown. In the two LED
configuration the link and the
activity functions share an
indicator. In this scheme the
LINK LED would flash LOW
each time activity is detected.
LED
This capacitor is normally not installed; however a placement can be provided.
It might need to be placed based on the results of FCC conformance testing. If it
is required, values in the pico fared range can be used. Large capacitance values
installed in this location can have a negative effect on long cable performance. So care
must be taken in selecting the values used.
8-22 pF
Keep trace length from magnetics to RJ-45 connector under one inch.
TDP C13
TDN C14
RDP E13
RDN E14
82551IT
Keep all termination resistors as
close to the 82551 as possible.
0.1 uF
Termplane
Use plane for
this signal to
make a board
capacitor.
Termplane
CGND = Chassis ground
Use plane for this signal
pF
Optional capacitor
0.1 uF
0.1 uF
RECEIVE
Create termination plane in PCB. This plane
acts as a path for low-frequency noise that
to help with EFT
conformance.
uF
RD+ 1
7 RX+
might be coupled to unused pins. The plane
should not have any direct connection.
5 CT
RD- 2
RDC 3
6 RX-
RD+ 1
MDI-X Mode Only
7 RX+
TD+ 16
TDC 14
TD- 15
1:1
TXCT
75 Ohms
TRANSMIT
MDI Mode Only
10 TX+
11 TX-
1500pF
2kV
RD- 2
TD- 15
TD+ 16
1:1
RECEIVE
1:1
TRANSMIT
6 RX-
11 TX-
10 TX+
3VSB
4.7uF
4.7uF
0.1uF
0.1uF
0.1uF 0.1uF
0.1uF
0.1uF
0.1uF
0.1uF
0.1uF 0.1uF
Place decoupling capacitors as close to the 82551 as possible. If component placements
are used on the bottom side of the board, then place decoupling under the 82551IT.
Figure 31. Reference Schematic Layout (Sheet 1 of 2)
Datasheet
95