LAN83C180 Datasheet, PDF (6/10 Pages) SMSC Corporation – 10/100 FAST ETHERNET PHY TRANSCEIVER

Migrating from the LAN83C180 10/100 PHY to the LAN83C185 10/100 PHY
4 Cable Interface
The requirements for the cable interface, including the magnetics and RJ45 connector interfaces, are
outlined in the sections below.
4.1 Magnetics
The LAN83C185 Phy Customer Reference Design uses the Bel S558-5999-46 magnetics module, which
replaces the magnetics module originally specified in the LAN83C180 Customer Reference design. Please
refer to SMSC Application Note 8.13 - "Suggested Magnetics" for a listing of currently approved magnetics,
and to the LAN83C185 MII Customer Reference Board (Assy. 6316) schematic for details.
4.2 Connector (RJ45) Interface
All connections between the RJ45 connector and magnetics module for the LAN83C185 remain identical to
LAN83C180.
4.3 Transmit & Receive Terminations
4.3.1
Transmit Terminations
The LAN83C185 transmit signals (TXP, TXN) should be pulled to +3.3V supplied from the board’s power
plane via a ferrite bead and termination resistors R_Term (see Figure 4.1 below). Power is supplied to the
transmitter via the 10-Ohm resistor and the transformer center tap.
+3.3V
FB1
R1_TERM
R2_TERM
TXP
LAN83C185
TXN
R3
10 Ohm
TD+
TCT
TD-
Magnetics Module
Transmit Channel
TX+
TCMT
TX-
C1
0.022 uF
Figure 4.1 - Tx to Magnetics Interface
SMSC AN 10.13
Page 6
APPLICATION NOTE
Revision 1.2 (07-12-04)