AN3007

Telecom disturbances

Doc ID 16018 Rev 1

3/20

1

Telecom disturbances

Figure 2 shows the previous Ethernet network when it is submitted to disturbances. These

transients are mainly due to two kinds of disturbance. The first one occurs on outside lines

and is linked to atmospheric effects (lightning). The second one happens on inside lines and

is due to electrostatic discharge (ESD). Today, tests for withstanding these disturbances are

defined in international standards.

Figure 2.

Line disturbance and protection location

The standard used to qualify Ethernet equipment against lightning strikes is the

IEC 61000-4-5 standard. This recommendation is based on the 1.2 / 50 µs – 8 / 20 µs

combination waveform (1.2 / 50 µs open-circuit voltage waveform and a 8 / 20 µs short-

circuit current waveform).

In Ethernet applications, Level 2 of this standard, which corresponds to 1 kV, is the most

often required. The test series resistance to be considered is 42

Ω (40 + 2 Ω of generator

internal resistance). Then, the equipment has to withstand a current of 24 A.

Figure 3, Table 1, and Figure 4 present the IEC 61000-4-5 surge test definition. First, a

simplified circuit of the 1.2 / 50 µs – 8 / 20 µs combination wave generator is shown

(Figure 3), then a table providing the open-circuit test voltage for each test level of the

standard (Table 1), and finally an example of a test setup (Figure 4).

Figure 3.

Simplified circuit of the combination wave generator (1.2/50 µs - 8/20 µs)

Hub

Ethernet card

Lightning

and

ESD

Protection

R4

R3

C

U

R1

R2

L