XRT83VSH28IB-F View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT83VSH28IB-F' PDF : 74 Pages View PDF
PRELIMINARY
XRT83VSH28
REV. P1.0.0
8-CHANNEL E1 SHORT-HAUL LINE INTERFACE UNIT
4.2.4 N+1 Redundancy Using External Relays
N+1 redundancy has one backup card for N primary cards. Due to impedance mismatch and signal contention,
external relays are necessary when using this redundancy scheme. The relays create complete isolation
between the primary cards and the backup card. This allows all transmitters and receivers on the primary cards
to be configured in internal impedance, providing one bill of materials for all interface modes of operation. The
transmit and receive sections of the LIU device are described separately.
4.2.5 Transmit Interface with N+1 Redundancy
For N+1 redundancy, the transmitters on all cards should be programmed for internal impedance. The
transmitters on the backup card do not have to be tri-stated. To swap the primary card, close the desired
relays, and tri-state the transmitters on the failed primary card. A 0.68uF capacitor is used in series with TTIP
for blocking DC bias. See Figure 26 for a simplified block diagram of the transmit section for an N+1
redundancy scheme.
FIGURE 26. SIMPLIFIED BLOCK DIAGRAM OF THE TRANSMIT INTERFACE FOR N+1 REDUNDANCY
Backplane Interface
Primary Card
XRT83VSH28
Tx
0.68uF
Internal
Impedence
Primary Card
XRT83VSH28
Tx
0.68uF
Internal
Impedence
Primary Card
XRT83VSH28
Tx
0.68uF
Internal
Impedence
Backup Card
XRT83VSH28
Tx
0.68uF
Internal
Impedence
Line Interface Card
1:2
1:2
1:2
E1 Line
E1 Line
E1 Line
36
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