SP3243EUEA-L-TR Datasheet, PDF (16/25 Pages) Exar Corporation – 3 Driver/5 Receiver Intelligent +3.0V to +5.5V RS-232 Transceivers

ESD Tolerance
The SP3243E series incorporates ruggedized
ESD cells on all driver output and receiver input
pins. The ESD structure is improved over our
previous family for more rugged applications
and environments sensitive to electro-static dis-
charges and associated transients. The improved
ESD tolerance is at least +15kV without damage
nor latch-up.
There are different methods of ESD testing ap-
plied:
a) MIL-STD-883, Method 3015.7
b) IEC61000-4-2 Air-Discharge
c) IEC61000-4-2 Direct Contact
The Human Body Model has been the generally
accepted ESD testing method for semi-con-
ductors. This method is also specified in
MIL-STD-883, Method 3015.7 for ESD testing.
The premise of this ESD test is to simulate the
human body’s potential to store electro-static
energy and discharge it to an integrated circuit.
The simulation is performed by using a test
model as shown in Figure 23. This method
will test the IC’s capability to withstand an ESD
transient during normal handling such as in
manufacturing areas where the ICs tend to be
handled frequently.
The IEC-61000-4-2, formerly IEC801-2, is gen-
erally used for testing ESD on equipment and
systems. For system manufacturers, they must
guarantee a certain amount of ESD protection
since the system itself is exposed to the outside
environment and human presence. The premise
with IEC61000-4-2 is that the system is required
to withstand an amount of static electricity when
ESD is applied to points and surfaces of the
equipment that are accessible to personnel dur-
ing normal usage. The transceiver IC receives
most of the ESD current when the ESD source
is applied to the connector pins. The test circuit
for IEC61000-4-2 is shown on Figure 24. There
are two methods within IEC61000-4-2, the Air
Discharge method and the Contact Discharge
method.
With the Air Discharge Method, an ESD voltage
is applied to the equipment under test (EUT)
through air. This simulates an electrically charged
person ready to connect a cable onto the rear of
the system only to find an unpleasant zap just
before the person touches the back panel. The
high energy potential on the person discharges
through an arcing path to the rear panel of the
system before he or she even touches the sys-
tem. This energy, whether discharged directly
or through air, is predominantly a function of
the discharge current rather than the discharge
voltage. Variables with an air discharge such as
approach speed of the object carrying the ESD
potential to the system and humidity will tend to
change the discharge current. For example, the
rise time of the discharge current varies with the
approach speed.
The Contact Discharge Method applies the ESD
current directly to the EUT. This method was
devised to reduce the unpredictability of the ESD
arc. The discharge current rise time is constant
since the energy is directly transferred without the
air-gap arc. In situations such as hand held sys-
tems, the ESD charge can be directly discharged
to the equipment from a person already holding
the equipment. The current is transferred on to
the keypad or the serial port of the equipment
directly and then travels through the PCB and
finally to the IC.
R_C
R_S
DC Power
Source
SW1
C_S
SW2
Device
Under
Test
Figure 23. ESD Test Circuit for Human Body Model
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
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SP3243E_102_060611