SP3203ECY-L Datasheet, PDF (12/16 Pages) Exar Corporation – 3V RS-232 Serial Transceiver with Logic Selector and 15kV ESD Protection

ESD Tolerance
The SP3203E incorporates ruggedized
ESD cells on all driver output and re-
ceiver input pins. The ESD structure is
improved over our previous family for more
rugged applications and environments
sensitive to electro-static discharges and
associated transients. The improved ESD
tolerance is at least +15kV without damage
nor latch-up.
There are different methods of ESD testing
applied:
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 semiconductors. 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 11. This method will test the IC’s
capability to withstand an ESD transient
during normal handling such as in manu-
facturing areas where the IC's tend to be
handled frequently.
The IEC-61000-4-2, formerly IEC801-2, is
generally 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 ex-
posed 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
during 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 12. 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 unpleas-
ant 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 system. 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 situ-
ations such as hand held systems, 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.
Figure 11. ESD Test Circuit for Human Body Model
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • [phone] • www.exar.com
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