EPT7055A Datasheet, PDF (2/2 Pages) PCA ELECTRONICS INC. – Token Ring Transceiver Module

ELECTRONICS INC.
Token Ring Transceiver Module
EPT7055A
The circuit below is a guideline for interconnecting PCA’s EPT7055A with a typical Token Ring PHY chip for 4 Mb/16Mb
applications over 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 TI380C60.
Typical insertion loss of the isolation transformer is 0.5dB up to 16 MHz. Under terminated conditions, to transmit a 2V pk-
pk signal across the cable, you must adjust the specific chip preset template control resistors to get at least 2.12V pk-pk
across the transmit input pins.
Note that there is no need for the receiver side filtering. So consider this a cost effective solution for almost all Token Ring
applications using this 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 return 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 of EPT7055A. 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 Connection to TI380C60 (or Equivalent)
RCVINA ₃₈
RCVINB
37
+5V
PHOUTA
29
PHOUTB
27 10µF
TMS38060
6
8
+5V
10µF
50Ω/2W
9
50Ω/2W
10
12
5 _Xmit±
11
4
RJ45
14
3 _Rcv±
13
6
127 8
DROUTB ₃₁
DROUTA
32
100Ω
100Ω
2 _EPT7055A
11
Common Mode
4
7
5
PCA ELECTRONICS, INC.
16799 SCHOENBORN ST.
NORTH HILLS, CA 91343
Notes : 1. Current limiting resistors R1 & R2 are included in this package.
CST7055Ab Rev. D 6/2/97
TEL: [phone]
FAX: [phone]
http://www.pca.com