XRT73LC00 datasheet(33/53 Pages) EXAR

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XRT73LC00

E3/DS3/STS-1 LINE INTERFACE UNIT

PRELIMINARY

REV. P1.0.1

Design Considerations for DS3 and STS-1 Appli-

cations

When installing equipment into environments as de-

picted in Figure 18, the system installation personnel

may be able to determine the cable length between

the local terminal equipment and the DSX-3/STSX-1

Cross-Connect Patch-Panel. The cable length be-

tween the local terminal equipment and the DSX-3/

STSX-1 Cross-Connect Patch Panel ranges between

0 and 450 feet.

It is extremely unlikely that the system installation

personnel will know the cable length between the

DSX-3/STSX-1 Cross-Connect Patch-Panel and the

remote terminal equipment. We recommend that the

Receive Equalizer be enabled by setting the REQDIS

input pin or bit-field to "0".

The only time the Receive Equalizer should be dis-

abled is when there is an off-chip equalizer in the Re-

ceive path between the DSX-3/STSX-1 Cross-Con-

nect and the RTIP/RRING input pins or, in applica-

tions where the Receiver is monitoring the transmit

output signal directly.

3.2.1.1.2

Design Considerations for E3 Appli-

cations

In E3 system installation, it is recommended that the

Receive Equalizer of the XRT73LC00 be enabled by

pulling the REQDIS input pin to GND or by setting the

REQDIS bit-field to “0”.

NOTE: The results of extensive testing indicates that when

the Receive Equalizer is enabled, the XRT73LC00 is capa-

ble of receiving an E3 line signal with anywhere from 0 to

12dB of cable loss over the Industrial Temperature range.

Design Considerations if the Overall Cable

Length is known

If during system installation the overall cable length is

known, then in order to optimize the performance of

the XRT73LC00 in terms of receive intrinsic jitter,

etc., the Receive Equalizer should be enabled or dis-

abled based upon the following recommendations:

The Receive Equalizer should be turned ON if the

Receive Section is going to receive a line signal with

an overall cable length of 300 feet or greater. The Re-

ceive Equalizer should be turned OFF if the Receive

Section is going to receive a line signal over a cable

length of less than 300 feet.

FIGURE 19. THE TYPICAL APPLICATION FOR THE SYSTEM INSTALLER

DSX-3

STSX-1

Digital Cross-

Connect System

Transmitting

Terminal

Receiving

Terminal

0 to 450 feet of

Cable

Pulses that are

compliant to the

Isolated DSX-3 or

STSX-1 Pulse

Template

Requirement

0 to 450 feet of

Cable

XRT73LC00 Datasheet(PDF) 33 Page - Exar Corporation

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