ADM488/ADM489

–9–

REV. 0

The fast transient burst test, defined in IEC1000-4-4, simulates

this arcing and its waveform is illustrated in Figure 20. It

consists of a burst of 2.5 kHz to 5 kHz transients repeating at

300 ms intervals. It is specified for both power and data lines.

Four severity levels are defined in terms of an open-circuit volt-

age as a function of installation environment. The installation

environments are defined as

1. Well-protected

2. Protected

3. Typical Industrial

4. Severe Industrial

300ms

16ms

V

t

V

0.2/0.4ms

t

5ns

50ns

Figure 20. IEC1000-4-4 Fast Transient Waveform

Table III shows the peak voltages for each of the environments.

Table III.

Level

PSU

I-O

1

0.5

0.25

2

1

0.5

32

1

44

2

A simplified circuit diagram of the actual EFT generator is

illustrated in Figure 21.

These transients are coupled onto the signal lines using an EFT

coupling clamp. The clamp is 1 m long and completely sur-

rounds the cable, providing maximum coupling capacitance

(50 pF to 200 pF typ) between the clamp and the cable. High

energy transients are capacitively coupled onto the signal lines.

Fast rise times (5 ns) as specified by the standard result in very

effective coupling. This test is very severe since high voltages are

coupled onto the signal lines. The repetitive transients can often

cause problems, where single pulses do not. Destructive latchup

may be induced due to the high energy content of the transients.

Note that this stress is applied while the interface products are

powered up and are transmitting data. The EFT test applies

hundreds of pulses with higher energy than ESD. Worst case

transient current on an I-O line can be as high as 40 A.

HIGH

VOLTAGE

SOURCE

50

OUTPUT

Figure 21. EFT Generator

Test results are classified according to the following:

1. Normal performance within specification limits.

2. Temporary degradation or loss of performance that is self-

recoverable.

3. Temporary degradation or loss of function or performance

that requires operator intervention or system reset.

4. Degradation or loss of function that is not recoverable due to

damage.

The ADM488/ADM489 has been tested under worst case con-

ditions using unshielded cables, and meets Classification 2 at

severity Level 4. Data transmission during the transient condi-

tion is corrupted, but it may be resumed immediately following

the EFT event without user intervention.

RADIATED IMMUNITY (IEC1000-4-3)

IEC1000-4-3 (previously IEC801-3) describes the measurement

method and defines the levels of immunity to radiated electro-

magnetic fields. It was originally intended to simulate the elec-

tromagnetic fields generated by portable radio transceivers or

any other device that generates continuous wave radiated electro-

magnetic energy. Its scope has since been broadened to include

spurious EM energy, which can be radiated from fluorescent

lights, thyristor drives, inductive loads, etc.

Testing for immunity involves irradiating the device with an EM

field. There are various methods of achieving this including use

of anechoic chamber, stripline cell, TEM cell and GTEM cell.

These consist essentially of two parallel plates with an electric

field developed between them. The device under test is placed

between the plates and exposed to the electric field. There are

three severity levels having field strengths ranging from 1 V to

10 V/m. Results are classified as follows:

1. Normal Operation.

2. Temporary Degradation or loss of function that is self-

recoverable when the interfering signal is removed.

3. Temporary degradation or loss of function that requires

operator intervention or system reset when the interfering

signal is removed.

4. Degradation or loss of function that is not recoverable due to

damage.