XRT73L03 Datasheet, PDF (38/62 Pages) Exar Corporation – 3 CHANNEL E3/DS3/STS-1 LINE INTERFCE UNIT

XRT73L03 3 CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT
REV. P1.0.13
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PRELIMINARY
3.2 THE RECEIVE EQUALIZER BLOCK
The purpose of this block is to equalize the incoming
distorted signal due to cable loss. The Receive
Equalizer attempts to restore the shape of the line
signal so that the transmitted data and clock can be
recovered reliably.
FIGURE 19. THE TYPICAL APPLICATION FOR THE SYSTEM INSTALLER
Transmitting
Terminal
0 to 450 feet of
Cable
Digital Cross-Connect
System
DSX-3
or
STSX-1
Pulses that are
compliant to the
Isolated DSX-3 or
STSX-1 Pulse Template
Requirement
0 to 450 feet of Cable
Receiving
Terminal
• Design Considerations for DS3 and STS-1
Applications
When installing equipment into environments depict-
ed in Figure 19, we recommend that the Receive
Equalizer be enabled by setting the REQDIS(n) input
pin for Channel(n) or the respective bit-fields to "0".
The only time that the Receive Equalizer should be
disabled is when an off-chip equalizer is in the Re-
ceive path between the Digital Cross-Connect system
and the RTIP/RRing input pins, or in applications
where the Receiver is monitoring the transmit output
signal directly.
• Design Considerations for E3 Applications or if
the Overall Cable Length is known
Figure 19 indicates the following:
a. The length of cable between the Transmitting Ter-
minal and the Digital Cross-Connect system can
range between 0 and 450 feet.
b. The length of cable between the Digital Cross-Con-
nect system and the Receive Terminal can range be-
tween 0 and 450 feet.
Consequently, the overall cable length between the
Transmitting Terminal and the Receiving Terminal can
range between very short cable length (e.g., near 0
feet) up to 900 feet.
If during System Installation the overall cable length is
known, to optimize the performance of the XRT73L03
in terms of receive jitter performance, etc., enable or
disable the Receive Equalizer based upon the follow-
ing recommendations:
The Receive Equalizer should be turned ON if the
Receive Section of a given channel is going to re-
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