XRT73L03A Datasheet, PDF (37/62 Pages) Exar Corporation – 3 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT

XRT73L03A
3 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
REV. 2.0.4
3.0 THE RECEIVE SECTION
Figure 13 indicates the Receive Section consists of
the following blocks:
• AGC/Equalizer
• Peak Detector
• Slicer
• Clock Recovery PLL
• Data Recovery
• HDB3/B3ZS Decoder
The purpose of the Receive Section is to take an in-
coming attenuated/distorted bipolar signal from the
line and encode it back into the TTL/CMOS format
where it can be received and processed by the Termi-
nal Equipment.
3.1 INTERFACING THE RECEIVE SECTIONS OF THE
XRT73L03A TO THE LINE
The design of the Receive Circuitry allows for trans-
former-couple or capacitive-couple the Receive Sec-
tion to the line. The specification documents for E3,
DS3, and STS-1 all specify 75 Ohm termination loads
when transmitting over coaxial cable. The recom-
mended method to interface the Receive Section to
the line in a manner is shown in Figure 22 and Figure
23.
FIGURE 22. RECOMMENDED SCHEMATIC FOR INTERFACING THE RECEIVE SECTION OF THE XRT73L03A TO
THE LINE (TRANSFORMER-COUPLING)
RxPOS_(n)
RxNEG_(n)
RxClk_(n)
RTIP_(n)
Channel (n)
RPOS_(n)
RNEG_(n)
RxClk_(n)
R1
37.4Ω
R2
37.4Ω
RRing_(n)
Only One Channel Shown
C1
0.01uf
J1
T1
BNC
1:1
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