EPA2116G Datasheet, PDF (2/2 Pages) PCA ELECTRONICS INC. – 10Base-T Interface Module with Enhanced CMA and Resistor Network

ELECTRONICS INC.
10Base-T Module with
Enhanced Common Mode Attenuation
EPA2116G
The circuit below is a guideline for interconnecting PCA’s EPA2116G with AMD 79C96X and -970, PCnet chip family as
reference controllers. Further details of system design, such as chip pin-out, etc. can be obtained from the specific chip
manufacturer.
Typical insertion loss of the isolation transformer/filter is 0.7dB. This parameter covers the entire spectrum of the encoded
signals in 10 Base-T protocols. However, the predistortion resistor network introduces some loss which has to be taken
into account in determining how well your design meets the Standard Template requirements.
Users are encouraged to verify if this network best suits their application needs with the chip manufacturer before choosing
a specific set of values. Additionally, user should make sure that these resistor values provide 802.3 Return Loss
specification complaince at either extremes of the cable impedance, namely; 85Ω to 115Ω. Implement only those parts in
the design that will meet this requirement.
A quick calculation of the effective Thevenin’s termination impedance for the filter follows:
R(termination)= 2(61.9//422)//1.2K≈100Ω.
Thus, when measuring the return loss of these parts on the bench, it is not necessary to provide a shunting resistor across
the four outputs.
The phantom resistors shown around the RJ45 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 0.08 inches away from the chip side pins of EPA2116G. There need not be any ground plane beyond
this point.
For best results, PCB designer should design the outgoing traces preferably to be 50Ω, balanced and well coupled to
achieve minimum radiation from these traces.
Typical Application Circuit for UTP
10 Base-T
PHY
TX+
TXd+
TX-
TXd-
RX+
RX-
1
8
1 ^TX+
2
6 2 ^TX- _RJ45*
3
11 3 ^RX+
RX-
4
96
4578
14
EPA2116G
16
5
12
PCA ELECTRONICS, INC.
16799 SCHOENBORN ST.
NORTH HILLS, CA 91343
Chassis
Ground
Notes : * Pin-outs shown are for NIC configurations.
For Hubs and Repeaters swap pins 1-2 with pins 3-6.
CSA2116Gb Rev. A 2/18/98
TEL: [phone]
FAX: [phone]
http://www.pca.com