XRT73R12 datasheet(21/89 Pages) EXAR

21 / 89 page

XRT73R12

REV. 1.0.3

TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT

FUNCTIONAL DESCRIPTION

The XRT73R12 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 and Transmitters 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 providing 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.

With 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

Line Interface Card

Primary Line Card

Framer/

Mapper

LIU

Back

Plane

Mid

Plane

31.6

Ω

31.6

Ω

0.01

µF

0.01

µF

1:1

Redundant Line Card

Framer/

Mapper

LIU

31.6

Ω

31.6

Ω

0.01

µF

0.01

µF

37.5Ω

GND

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