1ꢀ5k EꢁD-ꢂrotected, +ꢀk Rꢁ-232 Transceivers
R
1M
R 1500Ω
D
C
I 100%
P
90%
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
I
r
DISCHARGE
RESISTANCE
CHARGE-CURRENT
LIMIT RESISTOR
AMPERES
HIGH-
VOLTAGE
DC
DEVICE
UNDER
TEST
C
s
100pF
STORAGE
CAPACITOR
36.8%
SOURCE
10%
0
TIME
0
t
RL
t
DL
CURRENT WAVEFORM
Figure 6b. Human Body Model Current Waveform
Figure 6a. Human Body ESD Test Model
I
R
50M to 100M
R 330Ω
D
C
100%
90%
DISCHARGE
RESISTANCE
CHARGE CURRENT
LIMIT RESISTOR
HIGH-
VOLTAGE
DC
DEVICE
UNDER
TEST
C
s
150pF
STORAGE
CAPACITOR
SOURCE
10%
Figure 7a. IEC1000-4-2 ESD Test Model
t
t = 0.7ns to 1ns
r
30ns
60ns
IEC1000-4-2
The IEC1000-4-2 standard covers ESD testing and
performance of finished equipmentꢁ it does not
specifically refer to integrated circuits. The
MAX202E/MAX203E–MAX213E, MAX232E/MAX241E
help you design equipment that meets level 4 (the
highest level) of IEC1000-4-2, without the need for
additional ESD-protection components.
Figure 7b. IEC1000-4-2 ESD Generator Current Waveform
The air-gap test involves approaching the device with a
charged probe. The contact-discharge method
connects the probe to the device before the probe is
energized.
Machine Model
The Machine Model for ESD tests all pins using a
200pF storage capacitor and zero discharge
resistance. Its objective is to emulate the stress caused
by contact that occurs with handling and assembly
during manufacturing. Of course, all pins require this
protection during manufacturing, not just RS-232 inputs
and outputs. Therefore, after PC board assembly, the
Machine Model is less relevant to I/O ports.
The major difference between tests done using the
Human Body Model and IEC1000-4-2 is higher pea5
current in IEC1000-4-2, because series resistance is
lower in the IEC1000-4-2 model. Hence, the ESD
withstand voltage measured to IEC1000-4-2 is
generally lower than that measured using the Human
Body Model. Figure 7b shows the current waveform for
the 85V IEC1000-4-2 level-four ESD contact-discharge
test.
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