Datasheet
the ESD that withstands voltage measured to IEC 1000-
4-2 is generally lower than that measured using the
Human Body Model. Figure 6a shows the IEEE 1000-4-
2 model and Figure 6b shows the current waveform for
the ±8kV IEC 1000-4-2 Level 4 ESD Contact-Discharge
test.
The Air-Gap Method 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 resis-
tance. Its objective is to emulate the stress caused not
only by RS-232 inputs and outputs, but also by contact
that occurs due to handling and assembling during
manufacturing. Therefore, after PC board assembly, the
Machine Model is less relevant to I/O ports.
MAX221E
±15kV ESD-Protected, +5V, 1µA, Single RS-232
Transceiver with AutoShutdown
8 _______________________________________________________________________________________
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
C
s
100pF
R
C
1MΩ R
D
1500Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
I
P
100%
90%
36.8%
t
RL
TIME
t
DL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
I
r
10%
0
0
AMPERES
t
r
= 0.7ns to 1ns
30ns
60ns
t
100%
90%
10%
I
PEAK
I
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
C
s
150pF
R
C
50MΩ to 100MΩ R
D
330Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 5a. Human Body ESD Test Model
Figure 6a. IEC 1000-4-2 ESD Test Model
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
Figure 5b. Human Body Model Current Waveform