DS26334 3.3V, 16-Channel, E1/T1/J1 Short/Long-Haul Line Interface Unit
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Table 5-6. LIU Front-End Values
MODE
COMPONENT
75
COAX, 120
100/110
TWISTED PAIR,
TWISTED PAIR
Tx Capacitance
Ct
560pF typical. Adjust for board parasitics for optimal return loss.
International Rectifier 11DQ04 or 10BQ060,
Motorola MBR0540T1
Tx Protection
Dt
1
Rx Transformer RTR 1:1
TFr
Tx Transformer 1:2
Rx Transformer RTR 1:2
Tx Transformer 1:2
Tx Decoupling (TVDDn)
Tx Decoupling (TVDDn)
Rx Decoupling (AVDD)
Rx Decoupling (AVDD)
Rx Termination
Rx Termination RTR 1:1
Rx Termination RTR 1:2
Voltage Protection
TFt
TFr
TFt
C1
C2
C3
C4
C5
1
Rt
1
Rt
1
TVS1
Pulse TX1475 (recommended for both short/long-haul modes),
Halo TG83-S005NU (recommended for short-haul only)
Pulse T1124 (0°C to +70°C),
Pulse T1114 (-40°C to 85°C)
Common decoupling for all 16 channels = 68 F.
Recommended decoupling per channel = 0.1 F.
Common decoupling for all 16 channels = 68 F.
Decouple all six pins separately with a 0.1 F capacitor.
Rx capacitance for all 16 channels = 0.1 F.
Needed two resistors for all modes = 60.4 ±1%.
Needed two resistors for all modes = 15.0 ±1%.
SGS-Thomson SMLVT 3V3 (3.3V Transient Suppressor)
1
Only use if necessary for application.
5.4.3 Dual Rail
Dual-rail mode consists of TPOS, TNEG and TCLK pins on the system side. NRZ data is sampled on the falling
edge of TCLK as shown in
Figure 9-12
.
Figure 9-12 The Zero substitution B8ZS or HDB3 is not allowed. The data that appears on the TPOS pin will be
output on TTIP and data on the TNEG will be output on TRING after pulse shaping. Single-Rail Select Register
(
SRMS)
is used for selection of dual-rail or single-rail mode. The data that arrives at the TPOS and TNEG can be
overwritten in the maintenance mode by setting the BERT Control Register (
BTCR
).
5.4.4 Single-Rail Mode
Single-rail mode consists of TPOS, TNEG and TCLK pins on the System side. NRZ data is sampled on the falling
edge of TCLK as shown in
Figure 9-12
. The Zero substitution B8ZS or HDB3 is allowed. The TPOS data will be
encoded in AMI or B8ZS/HDB3 format on the TTIP and TRING pins after pulse shaping. Single-Rail Mode Select
(
SRMS)
is used for selection of dual-rail or single-rail mode. The data that arrives at the TPOS can be overwritten
in the maintenance mode by setting in BERT Control Register (
BTCR
).
5.4.5 Zero Suppression—B8ZS or HDB3
B8ZS coding is available when the device is in T1 mode (selected by TS2, TS1 and TS0 bits in the
TS
register).
B8ZS/HDB3 coding are enabled by default in single-rail mode. Setting the LCS bit in the
LCS
Register disables
B8ZS/HDB3. Note that if the individual LIU is configured in E1 mode then HDB3 code substitution will be selected.
Bipolar violations can be inserted via the BEIR register or Transmit Maintenance Register settings only if B8ZS or
HDB3 coding is turned off.
B8ZS substitution is defined in ANSI T1.102 and HDB3 in ITUT G.703 standards.
5.4.6 Transmit Power-Down
The transmitter will be powered down if the relevant bits in the
TPDE
are set. The TTIP/TRING outputs will be high
impedance when TPDE is set.