XR-T5684 View Datasheet(PDF) - Exar Corporation
Part Name
Description
Manufacturer
XR-T5684 Datasheet PDF : 16 Pages
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XR-T5684
Another function of the receiver is the signal quality
monitor that reports loss of signal when the input level on
RTIP and RRING falls below 0.4V or upon detection of
175 ± 15 consecutive zeros in the incoming data stream.
The zero detection circuit is active only when LCLK clock
is applied. In both cases, the receiver reports loss of
signal by setting LOS high, and at the same time, RPOS
and RNEG are forced to low. Under the loss of signal
conditions, the receiver will continue to recover data and
will return to its normal operation if a valid data is detected
on RTIP and RRING.
TRANSMITTER
The transmitter is designed to take dual rail NRZ data, plus a
synchronized input clock and produces a bipolar signal with
the appropriate shape for transmission to the line.
After sampling by the falling edge of TCLK, TPOS and
TNEG data are processed by a digital to analog converter
together with a slew-control circuit to generate output
pulses at TTIP and TRING with the appropriate amplitude
and shape to meet the cross-connect template specified
in CB 119. A typical output pulse is shown in Figure 7. In
order to meet the amplitude requirement with a single +5V
supply, the transmit signal is driven to the line differentially
via a 1:1.36 step-up transformer.
Pulse shaping is selectable through input control pins
LEN2, LEN1 and LEN0 for line lengths ranging from 0 to
655 feet of ABAM cable as illustrated in Table 1.
LEN2
0
1
1
1
1
LEN1
1
0
0
1
1
LEN0
1
0
1
0
1
Line Length Selected (ft.)
0 - 133
133 - 266
266 - 399
399 - 533
533 - 655
Table 1. ABAM or ALVYN Cable Type
Line Length Selection
The transmitter can be set to transmit a continuous AMI
encoded all ones signal to the line by forcing TAOS high. In
this mode, input data TPOS and TNEG are ignored and the
frequency of the transmitted signal is determined by TCLK.
With TTIP connected to MTIP and TRING connected to
MRING, the driver monitor can detect a non-functional T1
transmitter by monitoring the activity at its input. If no signal
is presented on MTIP and MRING for 63 TCLK clock cycles,
DPM goes high until the next AMI signal is detected.
T5684 Output Pulse Shape
1.0
CB119 Specification
0.5
0
-0.5
250
500
750
1000
Time (Nanoseconds)
Figure 7. Receiver Clock and Data Switching Characteristics
Rev 1.01
10
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