Datasheet

DS2155
157 of 238
Figure 24-4. Software-Selected Termination, Longitudinal Protection
T2
2:1
TTIP
DV SS
Dallas Semiconductor
T1/E1/J1 SCT or LIU
S2
F1
F2
TRING
DV DD
TV SS
TV DD
RV SS
RV DD
0.01 µF
2
0.1 µF
2
0.1 µF
2
0.1 µF
2
VCC
68 µF
2
VCC
RTIP
RRING
VCC
60 Ω60 Ω
1:1
S1
0.1 µF
S3
S4
S7
T1
1.0 µF
F3
F4
S5
S6
S8
T3
1
T4
1
1
Choke is optional but should be included when necessary f or common mode noise reduction.
2
Decoupling capacitors need to be placed near dev ice power pins
Des ign Notes:
100/110/120 Ω
Tw isted Pair
100/110/120 Ω
Tw isted Pair
Table 24-B. Component List (Software-Selected Termination, Longitudinal
Protection)
NAME DESCRIPTION
F1 to F4 1.25A slow blow fuse
S1 and S2 25V (max) transient suppressor
S3, S4, S5, S6 180V (max) transient suppressor
S7 and S8 40V (max) transient suppressor
T1 and T2 Transformer 1:1CT and 1:2CT (3.3V, SMT)
T3 and T4 Dual common-mode choke (SMT)
Note 1:
T3 and T4 are optional. For more information, contact the Telecom Support Group at
[e-mail]
.
Note 2:
A list of alternate transformer part numbers and manufacturers is available at
[e-mail]
.
Note 3:
The layout from the transformers to the network interface is critical. Traces should be at least 25
mils wide and separated from other circuit lines by at least 150 mils. The area under this portion
of the circuit should not contain power planes.
Note 4:
Some T1 (never in E1) applications source or sink power from the network-side center taps of
the Rx/Tx transformers.
Note 5:
The ground trace connected to the S2/S3 pair and the S4/S5 pair should be at least 50 mils wide
to conduct the extra current from a longitudinal power-cross event.