XRT75L02 View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT75L02' PDF : 50 Pages View PDF
xr
REV. 1.0.3
XRT75L02
TWO CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER
For E3 rate, since the output pulse template is measured at the secondary of the transformer and since there is
no Cross-Connect system pulse template requirements, the Transmit Build Out Circuit is always disabled.
4.3.1 Guidelines for using Transmit Build Out Circuit:
If the distance between the transmitter and the DSX3 or STSX-1, Cross-Connect system, is less than 225 feet,
enable the Transmit Build Out Circuit by setting the TxLEV_n input pin “Low” (in Hardware Mode) or setting the
TxLEV_n control bit to “0” (in Host Mode).
If the distance between the transmitter and the DSX3 or STSX-1 is greater than 225 feet, disable the Transmit
Build Out Circuit.
4.3.2 Interfacing to the line:
The differential line driver increases the transmit waveform to appropriate level and drives into the 75Ω load as
shown in Figure 6.
4.4 Transmit Drive Monitor:
This feature is used for monitoring the transmit line for occurrence of fault conditions such as a short circuit on
the line or a defective line driver.
To activate this function, connect MTIP_n pins to the TTIP_n lines via a 270 Ω resistor and MRing_n pins to
TRING_n lines via 270 Ω resistor as shown in Figure 16.
FIGURE 16. TRANSMIT DRIVER MONITOR SET-UP.
TTIP(n)
R1
31.6Ω +1%
TxPOS(n)
TxNEG(n)
TxLineClk(n)
TPOS(n)
TNEG(n)
TxCLK(n)TRING(n)
RxB
MTIP(n)
R4 270Ω
RxA
MRING(n)
R5 270Ω
XRT75L02 (0nly one channel shown)
R2
31.6Ω + 1%
R3
75Ω
1:1
When the MTIP_n and MRING_n are connected to the TTIP_n and TRING_n lines, the drive monitor circuit
monitors the line for transitions. The DMO_n (Drive Monitor Output) will be asserted “Low” as long as the
transitions on the line are detected via MTIP_n and MRING_n.
If no transitions on the line are detected for 128 ± 32 TxClk_n periods, the DMO_n output toggles “High” and
when the transitions are detected again, DMO_n toggles “Low”.
NOTES:
1. The Drive Monitor Circuit is only for diagnostic purpose and does not have to be used to operate the transmitter.
2. With TxMON pin “High”, MTIP and MRING will be internally connected to TTIP and TRING for self-monitoring.
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