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DS26324 3.3V, 16-Channel, E1/T1/J1 Short-Haul Line Interface Unit
26 of 120
Table 5-5. LIU Front-End Values
MODE
COMPONENT
75
COAX, 120 TWISTED PAIR,
100/110
TWISTED PAIR
Tx Capacitance
Ct
560pF typical. Adjust for board parasitics for optimal return loss.
Tx Protection
Dt
1
International Rectifier 11DQ04 or 10BQ060,
Motorola MBR0540T1
Rx Transformer RTR 1:1
TFr
Pulse TX1475
Tx Transformer 1:2
TFt
Halo TG83-S005NU
Rx Transformer RTR 1:2
TFr
Pulse T1124 (0°C to +70°C),
Pulse T1114 (-40°C to 85°C)
Tx Transformer 1:2
TFt
Tx Decoupling (TVDDn)
C1
Common decoupling for all 16 channels = 68
F.
Tx Decoupling (TVDDn)
C2
Recommended decoupling per channel = 0.1
F.
Rx Decoupling (AVDD)
C3
Common decoupling for all 16 channels = 68
F.
Rx Decoupling (AVDD)
C4
Decouple all six pins separately with a 0.1
F capacitor.
Rx Termination
C5
1
Rx capacitance for all 16 channels = 0.1
F.
Rx Termination RTR 1:1
Rt
1
Need two resistors = 60.4
±1%.
Rx Termination RTR 1:2
Rt
1
Need two resistors = 15.0
±1%.
Voltage Protection
TVS1
SGS-Thomson SMLVT 3V3 (3.3V Transient Suppressor)
1Only use if necessary for application.
5.4.3
Transmit Dual-Rail Mode
Transmit dual-rail mode consists of the TPOS, TNEG, and TCLK pins on the system side. NRZ data is sampled on
B8ZS or HDB3 encoding is not available in transmit dual-rail mode. The data that appears on the TPOS and TNEG
pins is output on TTIP and TRING without any modification. The Single-Rail Mode 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
Transmit Single-Rail Mode
Transmit single-rail mode consists of the TPOS and TCLK pins on the system side (TNEG is not used.). NRZ data
is sampled on the falling edge of TCLK as shown in
Figure 9-12. The zero substitution B8ZS or HDB3 encoding is
allowed. The TPOS data is encoded in AMI or B8ZS/HDB3 format on the TTIP and TRING pins after pulse
shaping. The Single-Rail Mode Select Register
(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 Bit Error Rate Tester
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 only if B8ZS or HDB3 coding is turned off.
B8ZS substitution is defined in ANSI T1.102 and HDB3 in ITU-T 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.