XRT91L81IB View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT91L81IB' PDF : 40 Pages View PDF
PRELIMINARY
XRT91L81
2.488/2.666GBPS OC-48/STM-16 SONET/SDH TRANSCEIVER
REV. P1.0.3
2.0 RECEIVE SECTION
The receive section of XRT91L81 includes the differential limiting amplifier inputs RXINP/N, followed by the
clock and data recovery unit (CDR) and receive serial-to-parallel converter. The integrated limiting amplifier,
designed to be AC coupled at the input, allows the reception of differential signals as low as 10 mV-pp. The
receiver accepts the high speed Non-Return to Zero (NRZ) serial data at 2.488/2.666 Gb/s through the
differential limiting amplifier input interfaces RXINP/N. The clock and data recovery unit recovers the high-
speed receive clock from the incoming scrambled NRZ data stream. The recovered serial data is converted
into 4-bit-wide 622.08/666 Mb/s parallel data and presented to the RXD[3:0]P/N LVDS parallel interface. A
divide-by-4 version of the high-speed recovered clock RXCLKP/N, is used to synchronize the transfer of the 4-
bit RXD[3:0]P/N data with the receive portion of the Upstream device. Upon initialization or loss of signal or
loss of lock the 155.52/77.76 MHz (166/83.3 MHz) external reference clock is used to start-up the clock
recovery phase-locked loop for proper operation. A special loop-back feature can be configured when
RLOOPP is used in conjunction with de-jittered loop-time mode that allows the re-transmitted data to comply
with ITU and Bellcore jitter generation specifications.
2.1 Receive Serial Input
The receive serial inputs can be applied to either the primary or secondary inputs selected by RXSEL. If
RXSEL is pulled "Low", the primary channel RXI0P/N is active. If RXSEL is pulled "High", the secondary
channel RXI1P/N is active. The receive serial inputs should be AC coupled to an optical module or an
electrical interface. A simplified block diagram is shown in Figure 3.
FIGURE 3. RECEIVE SERIAL INPUT INTERFACE BLOCK
RXI0P
RXI0N
OC-48
Transceiver
0.1µF
0.1µF
Optical Module
NOTE: Some optical modules integrate AC coupled capacitors within the module. If so, the external AC coupled capacitors
are not necessary and can be excluded.
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