XRT82D20 Datasheet, PDF (16/27 Pages) Exar Corporation – SINGLE CHANNEL E1 LINE INTERFACE UNIT

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SINGLE CHANNEL LINE INTERFACE UNIT XRT82D20
REV. 1.0.7
1.4 INTERFACING THE TRANSMIT SECTION OF THE
XRT82D20 TO THE LINE
ITU-T G.703 specifies that the E1 line signal can be
transmitted over coaxial cable and terminated with
75Ω or transmitted over twisted-pair and terminated
with 120Ω.
In both applications (e.g., 75Ω or 120Ω, the user is ad-
vised to interface the Transmitter to the Line, in the
manner as depicted in Figure 10 and Figure 11, re-
spectively.
FIGURE 10. ILLUSTRATION OF HOW TO INTERFACE THE XRT82D20 TO THE LINE FOR 75 Ω APPLICATIONS AND 3.3V
OPERATION ONLY
75 Ω Coax
75 Ω
Signal
Source
75 Ω Coax
R Load
75 Ω
1:2
2:1
270 Ω
270 Ω
RTIP
Rxx Input
RRING
9.1 Ω
9.1 Ω
TTIP
Tx Output
TRING
RPOS/RData
RNEG/LCV
RClk
TVDD
AVDD
10µF
TxLEV
TGND
AGND
+3.3 V
0.1 µF
TNEG/CODE
TPOS/TData
TClk
14