SP207E Datasheet, PDF (10/16 Pages) Sipex Corporation – +5V High Performance RS232 Transceivers

RR_CC
DC Power
Source
SSWW11
Contact-Discharge Module
RR_SS
R_V
SSWW22
CC_SS
Device
Under
Test
RS and RV add up to 330Ω for IEC1000-4-2.
Figure 8. ESD Test Circuit for IEC1000-4-2
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 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 situations 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.
30A
15A
0A
t=0ns
t=30ns
t¥
Figure 9. ESD Test Waveform for IEC1000-4-2
The circuit model in Figures 7 and 8 represent the
typical ESD testing circuit used for all three
methods. The C_S is initially charged with the DC
power supply when the first switch (SW1) is on.
Now that the capacitor is charged, the second
switch (SW2) is on while SW1 switches off. The
voltage stored in the capacitor is then applied
through R_S, the current limiting resistor, onto the
device under test (DUT). In ESD tests, the SW2
switch is pulsed so that the device under test
receives a duration of voltage.
SP207EDS/09
SP207E Series High Performance RS232 Transceivers
10
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