CSF8116Sb

Rev. 1

4/17/98

10/100 Base-X Module for

Multi-Port Applications

EPF8116S

E L E C T R O N I C S I N C .

The circuit below is a guideline for interconnecting PCA’s EPF8116S with Level One LXT980, LXT974 and LXT975 chips for

10/100 Mb/s applications. Further details can be obtained from the chip manufacturer application notes.

Typical insertion loss of the isolation transformer is 0.5dB. This parameter covers the entire spectrum of the encoded

signals in 10/100 protocols. Under terminated conditions, to transmit a 2V pk-pk signal across the cable, you must adjust

the chips supporting resistor to get at least 2.12V pk-pk across the transmit pins.

Primary side center taps can be returned to the chip side ground plane; but more often than not, if the ground plane is itself

noisy, field experience has shown that it may worsen EMI situation. It is perhaps wiser to carefully lay the system borad

so that substantial gain in EMI suppression is obtained from the so called “common mode termination” on the cable side as

shown below. In any event, this configuration has been known to be quite successful in the field in EMI containment for

similar applications.

The phantom resistors shown around the connector have been known to suppress unwanted radiation that unused wires

pick up from the immediate environment. Their placement and use are to be considered carefully before a design is

finalized.

It is recommended that there be a neat separation of ground planes in the layout. It is generally accepted practice to limit

the plane off at least 0.05 inches away from the chip side pins of EPF8116S. There need not be any ground plane beyond

this plane.

For best results, PCB designer should design the outgoing traces preferably to be 50

Ω, balanced and well coupled to

achieve minimum radiation from these traces.

Typical Application Circuit for UTP (only one port shown)

TEL: (818) 892-0761

FAX: (818) 894-5791

http://www.pca.com

PCA ELECTRONICS, INC.

16799 SCHOENBORN ST.

NORTH HILLS, CA 91343

LXT

980

974

975

RJ45*

1

2

6

3

TPON1

TPOP1

TPIN1

TPIP1

EPF8116S

Rcv

Xmit

1

3

4

5

36

40

37

38

151

149

147

146

TD1-

TD1+

RD1-

RD1+

Rx1+

Rx1-

Tx1+

Tx1-

2

39

High Voltage

Capacitor

(2000 V)