EPT7008AG Datasheet, PDF (2/2 Pages) PCA ELECTRONICS INC. – Token Ring Transceiver Module

ELECTRONICS INC.
Token Ring Transceiver Module
EPT7008AG
The circuit below is a guideline for interconnecting PCA’s EPT7008AG 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 “current source” driver such as TMS38054. Only one type of cable
should be driven by the module: either UTP or STP. If you are using 120Ω 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 EPT7066 or similar parts optimized
for 120Ω cable.
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 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 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 EPT7008AG. There need not be any ground plane beyond
this point.
For best results, PCB designer should design the outgoing traces preferably to be 75Ω/50Ω, (as the case may be)
balanced and well coupled to achieve minimum radiation from these traces.
Typical Application Circuit Connection to TMS38054 (or Equivalent)
RCVINA ₃₈
RCVINB ₃₇
+5V
PHOUTA
29
PHOUTB
27 10µF
TMS38054
DROUTB ₃₁
DROUTA ₃₂
4
2
Vcc1
+5V_PHRET ¹
24
50Ω/2W
13
50Ω/2W
10µF
14
23
22
19 _Chassis
Ground
16
15
21
+5V
11
20
3
18
12 ^EPT7008AG 17
10
1(R)
5(B)
6(G)
DB-9
Connector
9(O)
Use only
one connector
4 Rcv±
5
RJ45
3 Xmit±
6
1 27 8
+5V
Notes : 1. Pin 24 is left unconnected. Applications vary. Your system may have a phantom
drive return detection circuit needing pin 24 to be connected separately.
2. Red line connections to DB-9 Connector are 75Ω impedance traces.
PCA ELECTRONICS, INC.
16799 SCHOENBORN ST.
NORTH HILLS, CA 91343
CST7008Ab Rev. - 10/2/96
TEL: [phone]
FAX: [phone]
http://www.pca.com