AN2064 - APPLICATION NOTE

3/14

The table 1 gives the main lightning standards.

Table 1: Main line card lightning surge standards

Main worldwide standards for 50/60Hz overvoltage disturbances can be defined by two parameters: the

applied RMS voltage, between 60V and 1000V, and the test duration, between 0.2s and 15min.

From this section we can conclude that the TRISIL current capability must be adapted according to the

specific country (for example, a waveform surge of 100A for 10/1000µs for the US). As TRISIL are

dedicated to manage high currents for short duration surges (in the range of hundreds of ms) the 50/60Hz

disturbances test requirements show the need of a complementary protection stage, implemented with

series protection devices like fuses or positive temperature coefficient resistors (PTC).

2. Protection circuit

In the protection circuit we find particularities linked to the characteristics already mentioned in the TRISIL

selection section and also linked to the CO line interface. Generally the subscriber line interface circuit

(SLIC) is directly connected to the line without any isolation stage when operating in analog mode, while

in digital applications isolation is achieved using

a transformer.

Please note that, at the CO side,

protection is split into two areas - the primary protection stage located in the MDF and the secondary

protection directly soldered on the subscriber line card.

Country

Standard

Surge voltage

Waveform

Current

Worldwide

ITU-T K20

1500V

10/700µs

37.5A

Worldwide

IEC-61000-4-5

1000/4000V

10/700µs

25/100A

Worldwide

IEC-61000-4-5

1000/4000V

1.2/50µs

25/100A

Germany

VDE0433

2000V

10/700µs

50A

Germany

VDE0878

2000V

1.2/50µs

50A

USA

GR-1089 Core (Telcordia)

2500V

2/10µs

500A

USA

GR-1089 Core (Telcordia)

1000V

10/1000µs

100A

France

I3124

1000V

0.5/700µs

25A

Figure 3: Analog line card protection circuit

SLIC

Ring generator

Tip

Ring

-V bat

Relay

PTC or Fuse

PTC or Fuse

TRISIL 1

TRISIL 1

TRISIL 2

TRISIL 2

Rs1

Rs1

Rs2

Rs2

Subscriber line card

Secondary protection, first stage Fuse or PTC and TRISIL 1, second stage TRISIL 2

-