ADM488 Analog Devices, ADM488 Datasheet - Page 9

• Manufacturer Part Number: ADM488
• Description: Full-Duplex/ Low Power/ Slew Rate Limited/ EIA RS-485 Transceivers
• Manufacturer: Analog Devices

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
Table III shows the peak voltages for each of the environments.
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.
REV. 0
Figure 20. IEC1000-4-4 Fast Transient Waveform
V
V
Level
1
2
3
4
5ns
0.2/0.4ms
V
PSU
0.5
1
2
4
300ms
PEAK
Table III.
(kV)
50ns
V
I-O
0.25
0.5
1
2
PEAK
16ms
(kV)
t
t
–9–
Test results are classified according to the following:
1. Normal performance within specification limits.
2. Temporary degradation or loss of performance that is self-
3. Temporary degradation or loss of function or performance
4. Degradation or loss of function that is not recoverable due to
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-
3. Temporary degradation or loss of function that requires
4. Degradation or loss of function that is not recoverable due to
recoverable.
that requires operator intervention or system reset.
damage.
recoverable when the interfering signal is removed.
operator intervention or system reset when the interfering
signal is removed.
damage.
VOLTAGE
SOURCE
HIGH
Figure 21. EFT Generator
R
C
C
C
ADM488/ADM489
L
Z
S
R
M
C
D
OUTPUT
50