22

20

18

16

14

12

10

8

6

4

2

0

Time - s

0

5

10

15

20

25

30

35

40

0.5kV Surge

10kV ESD

4kV EFT

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

Time - s

0

5

10

15

20

25

30

35

40

0.5kV Surge

6kV Surge

3.0

2.8

2.6

2.4

SN888C

SLLSEI4 – SEPTEMBER 2013

www.ti.com

The on-chip implementation of IEC ESD protection significantly increases the robustness of equipment. Common

discharge events occur because of human contact with connectors and cables. Designers may choose to

implement protection against longer duration transients, typically referred to as surge transients. Figure 10

suggests two circuit designs providing protection against short and long-duration surge transients, in addition to

ESD and Electrical Fast Transients (EFT) transients. Table 2 lists the bill of materials for the external protection

devices.

EFTs are generally caused by relay-contact bounce, or the interruption of inductive loads. Surge transients often

result from lightning strikes (direct strike or an indirect strike which induces voltages and currents), or the

switching of power systems, including load changes and short circuits switching. These transients are often

encountered in industrial environments, such as in factory automation and power-grid systems.

Figure 17 compares the pulse-power of the EFT and surge transients with the power caused by an IEC ESD

transient. In the diagram on the left of Figure 17, the tiny blue blip in the bottom left corner represents the power

of a 10-kV ESD transient, which is low compared to the significantly higher EFT power spike, and certainly lower

than the 500-V surge transient. This type of transient power is well representative of factory environments in

industrial and process automation. The diagram on the right of Figure 17 compares the enormous power of a 6-

kV surge transient, most likely occurring in e-metering applications of power generating and power grid systems,

with the aforementioned 500-V surge transient.

NOTE

The unit of the pulse-power changes from kW to MW, thus making the power of the 500-V

surge transient almost disappear from the scale.

Figure 17. Power Comparison of ESD, EFT, and Surge Transients

In the case of surge transients, hgih-energy content is signified by long pulse duration and slow-decaying pulse

power

The electrical energy of a transient that is dumped into the internal protection cells of the transceiver is converted

into thermal energy. This thermal energy heats the protection cells and literally destroys them, thus destroying

the transceiver. Figure 18 shows the large differences in transient energies for single ESD, EFT, and surge

transients as well as for an EFT pulse train, commonly applied during compliance testing.

14

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