EMC testing

AN3978

12/19

Doc ID 022179 Rev 1

4

EMC testing

The EMC requirements according to IEC61131-2 have been verified. Application tests

showed much better results than the requirements given by the industrial standard. The test

results are listed in the tables below. No additional protection devices have been used in the

application.

According to Table 1 and Table 2, it is clear that the chosen optical isolators functionality is

influenced by the burst noise. Therefore, performance criteria A is achieved with up to 3 kV

burst amplitude, the system then behaves according to criteria B.

A trial has been carried out and primary and secondary GNDs have been shorted in order to

limit common mode transients across the optical isolation. In this configuration the

performance criteria A is fulfilled also for higher burst amplitudes.

Therefore, the application designer should choose different isolators if a higher level of

immunity must be achieved. Selection should target isolators with a high CMR (“Common

Mode Rejection”) parameter.

Table 1.

Application EFT (burst) robustness, applied to supply voltage lines

Configuration

EFT test signal amplitude, test results at polarity (+ / -)

1 kV

2 kV

3 kV

4 kV

5 kV

Standard demonstration board

configuration

A / A

A / A

A / A

B / B

B / B

Primary and secondary GNDs shorted

A / A

A / A

A / A

A / A

A / A

Table 2.

Application EFT (burst) robustness, applied to output lines

Configuration

EFT test signal amplitude, test results at polarity (+ / -)

1 kV

2 kV

3 kV

4 kV

5 kV

Standard demonstration board

configuration

A / A

A / A

A / A

B / B

B / B

Primary and secondary GNDs shorted

A / A

A / A

A / A

A / A

A / A

Table 3.

Application surge test results, surge applied to supply lines

Configuration

Mode

Surge test signal amplitude, test results at polarity (+ / -)

1 kV

2 kV

3 kV

4 kV

Standard

demonstration

board configuration

Common (CM)

A / A

A / A

A / A

A / A

Differential (DM)

B / B

B / B

B / B

B / B