CSF8050Sb

Rev. Orig.

3/6/97

10/100 Base-X Module for

QSI 6611/6612

Multi-Port Applications

EPF8050S

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

The circuit below is a guideline for interconnecting PCA’s EPF8050S with QSI6611 and QSI6612 chip set 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.

It is recommended that system designers do not use the receiver side center tap to ground, via a capacitor. This may

worsen EMI, specifically if the secondary “common mode termination” is pulled to chassis ground as shown.

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.

The “common mode termination” load of 75

Ω shown from the center taps of the secondary may be taken to chassis ground

via a cap of suitable value. This depends upon user’s design, EMI margin etc.

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 EPF8050S. 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

TEL: (818) 892-0761

FAX: (818) 894-5791

http://www.pca.com

PCA ELECTRONICS, INC.

16799 SCHOENBORN ST.

NORTH HILLS, CA 91343

Notes : R = 80

Ω suggested; RC typical 39Ω. Consult QSI for update.

* NIC Side is shown. Hub side connection will have crossover swapping pins 3-6 &

QSI6611

or

QSI6612

RJ45*

1

2

6

3

4

5

7

8

TX+

TX-

RX+

RX-

Chassis

Ground

50

Ω

50

Ω

75

Ω

Node

Pinout

EPF8050S

High Voltage

Capacitor

40

39

38

36

37

3

5

1

2

4

25

Ω

25

Ω

CM Capacitor

Rcv

Xmit

R = 80 suggested