4.0 Applications
Bt8370/8375/8376
4.1 External Component Specifications
Fully Integrated T1/E1 Framer and Line Interface
Figure 4-1. Option A: Long Haul Application with Ground Reference on the Line Side (2 of 2)
NOTE(S):
(1)
Line side secondary surge protection to meet FCC Part 68, Bellcore TR-NWT-001089, and IEC 1000-4-5 requirements.
These components are: 1. TVS-LC01-6 Semtech, 2. PTC-TR600-160 Raychem, 3. TVS Thyristor—Teccor P3100SB.
A thyristor device (crow bar device) is used to protect against common mode (longitudinal) surges.
A Thyristor device with 275 V breakover voltage rated to handle 100A (tp = 10X100Us) is required.
A LC01-6 device provides protection during the metallic high surge lightning tests.
It is designed to shunt the surge current with a maximum clamping voltage of 16 V below the transformer saturation point.
The low capacitance characteristic of LC01-6 (50 pF) is required to avoid signal degration of the high speed digital pulse. A
PTC device is used for AC power cross faults, meeting the requirements of Bellcore 1089 and UL1459.
(2)
Chip side Secondary surge protection. Diodes should be low capacitance, fast turn-on Schottky or surge protection
diodes. These components are: 1. Schottky Diode—10BQ040(surface mount) or 11DQ04(discrete) International Rectifier
or one 20CJQ04 with two 10BQ040 2. two 2.1 Ω, 1/4 W, 1% Resistors. The two 470 Ω resistors in series with RTIP/RRING
are used to limit the current going into the device while the power is off and T1/E1 lines are connected.
Optional programmable receive termination –75/100/120 Ω.
Optional fixed transmit termination. The value shown provides acceptable transmit return loss for T1 and E1 applications.
(3)
(4)
(5)
Required fixed receive termination. The parallel combination of the fixed termination and programmable termination plus
series value of the primary surge protection line feed resistor (PTC) should match the line impedance required.
VSET Resistor. The VSET resistance value controls the transmit signal amplitude and depending on the line feed resistance
(6)
(PTC) in the primary surge protection circuit, its value can be fine-tuned. Use R (VSET) = 14 k if total line series resistance
is 0 to 12 Ω.
(7)
The Physical area between the connector and chokes should be kept small in order to avoid high frequency coupling and to
improve emissions test. Another good option is to place chokes between PTC and the Line side surge protection device. If
common mode noise is a concern then use the through hole package (PE65854) at the connector.
4-4
Conexant
N8370DSE
CONEXANT [ CONEXANT SYSTEMS, INC ]
