XRT59L921 Datasheet, PDF (23/32 Pages) Exar Corporation – TWENTY-ONE CHANNEL E1 LINE INTERFACE UNIT

XRT59L921
REV. 1.2.1
TWENTY-ONE CHANNEL E1 LINE INTERFACE UNIT
P.O. Box 5826
Redwood City, CA 94063
Tel: [phone]
FAX: [phone]
2.0 THE RECEIVE SECTION
The Receive Sections of the XRT59L921 consists of the following blocks:
• The Receive Equalizer block
• The Peak Detector and Slicer block
• The LOS Detector block
• The Receive Output Interface block
2.1 Interfacing the Receive Sections to the Line (Transformer Coupling)
The design of each channel (within the XRT59L921) permits the user to transformer-couple the Receive
Section to the line. Additionally, as mentioned earlier, the specification documents for E1 specify 75Ω
termination loads, when transmitting over coaxial cable, and 120Ω loads, when transmitting over twisted-pair.
Figure 9, and Figure 10 present the two methods that the user can employ in order to interface the Receivers
(of the XRT59L921) to the line.
FIGURE 9. RECOMMENDED SCHEMATIC FOR INTERFACING THE RECEIVE SECTIONS OF THE XRT59L921 TO THE
LINE FOR 75Ω APPLICATIONS (TRANSFORMER-COUPLING)
RxPOS_n
RxNEG_n
XRT59L921
RTIP_n
RxPOS_n
RxNEG_n
75 Ω
1:1
Coaxial cable
LOS_n
LOS_n
RRING_n
21