Datasheet

13
Date: 02/24/05 SP3222E, SP3232E True +3.0 to +5.0V RS-232 Transceivers © Copyright 2005 Sipex Corporation
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.
The circuit models in Figures 17 and 18
represent the typical ESD testing circuits 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.
R
C
C
S
R
S
SW1
SW2
R
C
Device
Under
Test
DC Power
Source
C
S
R
S
SW1
SW2
Figure 17. ESD Test Circuit for Human Body Model
R
S
and R
V
add up to 330Ω for IEC1000-4-2.
R
S
and R
V
add up to 330Ω for IEC1000-4-2.
Contact-Discharge Module
R
V
R
C
C
S
R
S
SW1
SW2
R
C
Device
Under
Test
DC Power
Source
C
S
R
S
SW1
SW2
R
V
Contact-Discharge Module
Figure 18. ESD Test Circuit for IEC1000-4-2