CST7068Gb

Rev. 1

7/7/98

Token Ring Front End Filter Module

Typical Application Circuit Connection to TI380C30 (or Equivalent)

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

EPT7068G

The circuit below is a guideline for interconnecting PCA’s EPT7068G with a typical Token Ring PHY chip for 4 Mb/16Mb

applications over STP or UTP cable.

Further details of system design should be obtained from the specific chip

manufacturer. Note that this module is optimized for a “voltage source” driver such as TI380C series. Only one type of

cable should be driven by the module: either UTP or STP. If you are using 120

Ω cable or desire to install only one RJ45

connector thus leaving the STP use with a dongle when needed, please refer to PCA part numbers EPT7069 or similar parts

optimized for 120

Ω cable.

Note that the receiver side filtering is identical, thus making it possible for use in a DTR application as well. Consider this a

cost effective solution for almost all Token Ring applications using this chip or similar chips.

The pull down resistors to chassis via a cap shown around the RJ45 connector have been known to suppress unwanted

radiation that unused wires pick up from the immediate environment. This is specially true if driving UTP cable. Their

placement and use are to be considered carefully before a design is finalized.

No specific recommendation is made here for phantom circuitry, implementation varies. Please note that additional

emission control has been observed if both nodes of the phantom bypass capacitor on the transmit channel are pulled to

the chassis ground via suitable capacitors.

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 EPT7068G. There need not be any ground plane beyond

this point.

For best results, PCB designer should design the outgoing traces preferably to be 75

Ω/50Ω, balanced and well coupled to

achieve minimum radiation from these traces.

Notes : 1. Suggested phantom circuit is for reference only. Applications Vary.

2. Phantom return on Rcv channel at pins 11 and 12 is not shown.

3. Your application may suffice by using an external inductor pulled to ground.

4. Red line connections to DB-9 Connector are 75

Ω impedance traces (if used).

5. C* : Primary center taps may be pulled to ground by Caps to enhance common mode attenuation.

TI380C30

RJ45

4

5

3

6

Rcv+

PHOUTA

Chassis

Ground

2

3

12

11

5(B)

9(O)

DB-9

Connector

9

Rcv-

PHOUTB

Xmit-

Xmit+

2

3

50

Ω/2W

50

Ω/2W

12

11

+5V

+5V

10µF

10µF

Use only

one connector

1(R)

6(G)

8

7

12

100

Ω

100

Ω

EPT7068G

13

10

14

9

6

4

Rcv Channel

EPT7068G

14

13

10

C*

6

4

Xmit Channel

Chassis

Ground

RSTP

TSTP

RU

TU

TEL: (818) 892-0761

FAX: (818) 894-5791

http://www.pca.com

PCA ELECTRONICS, INC.

16799 SCHOENBORN ST.

NORTH HILLS, CA 91343