BT8376EPF datasheet(270/323 Pages) CONEXANT

270 / 323 page

4.0 Applications

Bt8370/8375/8376

4.1 External Component Specifications

Fully Integrated T1/E1 Framer and Line Interface

4-6

Conexant

N8370DSE

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, or 1. Thyristor (Sidactor)—Teccor

P0300SB, 2. PTC-TR600-160 Raychem can be used.

An LC01-6 device provides protection during high surge lightning tests. It is designed to shunt the surge current with a

maximum clamping voltage of 16 V maximum, below the transformer saturation point.

A Thyristor (Sidactor—Teccor P0300SB) clamps the voltage at 40 V maximum.

A PTC device is used for 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—11DQ04 (disrete) or 10BQ040 (surface mount) International Rectifier,

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.

(3) Optional programmable receive termination –75/100/120

Ω.

(4) Optional fixed transmit termination. The value shown provides acceptable transmit return loss for T1 and E1 applications.

(5) Required fixed receive termination. The parallel combination of the fixed termination and programmable termination plus

the primary surge protection line feed resistor (PTC) must match the line impedance.

(6) VSET Resistor. The VSET resistance value controls the transmit signal amplitude and depending on the line feed resistance

(PTC) in the primary surge protection circuit, its value can be fine-tuned. Use R (VSET) = 14 k if total line feed 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 Line side surge protection device. If

common mode noise is a concern then use the through hole package (PE65854) at the connector.

Figure 4-2. Option B: Long Haul with No Ground Reference (2 of 2)

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