ADM483E
I-O lines are particularly vulnerable to ESD damage. Simply
touching or plugging in an I-O cable can result in a static
discharge that can damage or completely destroy the interface
product connected to the I-O port.
It is, therefore, extremely important to have high levels of ESD
protection on the I-O lines.
It is possible that the ESD discharge could induce latchup in the
device under test. It is therefore important that ESD testing on
the I-O pins be carried out while device power is applied. This
type of testing is more representative of a real world I-O
discharge where the equipment is operating normally when the
discharge occurs.
100%
90%
V
t
300ms
V
5ns
16ms
50ns
t
0.2/0.4ms
Figure 23. IEC1000-4-4 Fast Transient Waveform
Table V shows the peak voltages for each of the environments.
I
PEAK
Table V.
Level
36.8%
V
PEAK
(kV)
PSU
0.5
1
2
4
V
PEAK
(kV)
I-O
0.25
0.5
1
2
10%
TIME t
t
RL
t
DL
1
2
3
4
Figure 22. Human Body Model ESD Current Waveform
Table IV. ADM483E ESD Test Results
A simplified circuit diagram of the actual EFT generator is
illustrated in Figure 24.
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.
ESD Test Method
Human Body Model: Air
Human Body Model: Contact
I-O Pins
±
15 kV
±
8 kV
Other Pins
±
3.5 V
FAST TRANSIENT BURST IMMUNITY (IEC1000-4-4)
IEC1000-4-4 (previously 801-4) covers electrical fast-transient/
burst (EFT) immunity. Electrical fast transients occur as a
result of arcing contacts in switches and relays. The tests
simulate the interference generated when, for example, a power
relay disconnects an inductive load. A spark is generated due to
the well known back EMF effect. In fact, the spark consists of a
burst of sparks as the relay contacts separate. The voltage
appearing on the line, therefore, consists of a burst of extremely
fast transient impulses. A similar effect occurs when switching
on fluorescent lights.
The fast transient burst test, defined in IEC1000-4-4, simulates
this arcing and its waveform is illustrated in Figure 23. 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
voltage as a function of installation environment. The installa-
tion environments are defined as
1.
2.
3.
4.
Well-protected
Protected
Typical Industrial
Severe Industrial
HIGH
VOLTAGE
SOURCE
R
C
L
R
M
C
D
50Ω
OUTPUT
C
C
Z
S
Figure 24. 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.
–7–
REV. 0
AD [ ANALOG DEVICES ]
