XRT75R12 Datasheet, PDF (21/89 Pages) Exar Corporation – TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR

PRELIMINARY
TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR
XRT75R12
REV. P1.0.2
FUNCTIONAL DESCRIPTION
The XRT75R12 is a twelve channel fully integrated Line Interface Unit featuring EXAR’s R³ Technology
(Reconfigurable, Relayless Redundancy) for E3/DS3/STS-1 applications. The LIU incorporates 12
independent Receivers, Transmitters and Jitter Attenuators in a single 420 Lead TBGA package. Each
channel can be independently programmed to support E3, DS-3 or STS-1 line rates using one input clock
reference of 12.288MHz in Single Frequency Mode (SFM). The LIU is responsible for provding the physical
connection between a line interface and an aggregate mapper or framing device. Along with the analog-to-
digital processing, the LIU offers monitoring and diagnostic features to help optimize network design
implementation. A key characteristic within the network topology is Automatic Protection Switching (APS).
EXAR’s proven expertise in providing redundany solutions has paved the way for R³ Technology.
1.0 R³ TECHNOLOGY (RECONFIGURABLE, RELAYLESS REDUNDANCY)
Redundancy is used to introduce reliability and protection into network card design. The redundant card in
many cases is an exact replicate of the primary card, such that when a failure occurs the network processor
can automatically switch to the backup card. EXAR’s R³ technology has re-defined E3/DS-3/STS-1 LIU design
for 1:1 and 1+1 redundancy applications. Without relays and one Bill of Materials, EXAR offers multi-port,
integrated LIU solutions to assist high density aggregate applications and framing requirements with reliability.
The following section can be used as a reference for implementing R³ Technology with EXAR’s world leading
line interface units.
1.1 Network Architecture
A common network design that supports 1:1 or 1+1 redundancy consists of N primary cards along with N
backup cards that connect into a mid-plane or back-plane architecture without transformers installed on the
network cards. In addition to the network cards, the design has a line interface card with one source of
transformers, connectors, and protection components that are common to both network cards. Wtih this
design, the bill of materials is reduced to the fewest amount of components. See Figure 2. for a simplified
block diagram of a typical redundancy design.
FIGURE 2. NETWORK REDUNDANCY ARCHITECTURE
Framer/
Mapper
0.01µF
Rx _0.01µF
LIU
Tx
31.6Ω
31.6Ω
Primary Line Card
GND
37.5Ω
37.5Ω
1:1
1:1
Line Interface Card
Framer/
Mapper
0.01µF
Rx _0.01µF
LIU
Tx
31.6Ω
31.6Ω
Redundant Line Card
Back
Plane
or
Mid
Plane
18