Datasheet

MAX1406
Human Body Model
Figure 2a shows the Human Body Model, and Figure
2b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of inter-
est, which is then discharged into the device through a
1.5kresistor.
IEC1000-4-2
The IEC1000-4-2 standard covers ESD testing and per-
formance of finished equipment; it does not specifically
refer to integrated circuits. The MAX1406 helps you
design equipment that meets Level 4 (the highest level)
of IEC1000-4-2, without additional ESD-protection com-
ponents.
The main difference between tests done using the
Human Body Model and IEC1000-4-2 is higher peak
current in IEC1000-4-2 (Figure 3). Because series resis-
tance is lower in the IEC1000-4-2 ESD test model, the
ESD withstand voltage measured to this standard is
generally lower than that measured using the Human
Body Model. Figure 3b shows the current waveform for
the ±8kV IEC1000-4-2 Level 4 ESD Contact-Discharge
test.
The Air-Gap test involves approaching the device with
a charge probe. The Contact-Discharge method con-
nects the probe to the device before the probe is ener-
gized.
Machine Model
The Machine Model for ESD testing uses a 200pF stor-
age capacitor and zero-discharge resistance. It mimics
the stress caused by handling during manufacturing
and assembly. Of course, all pins (not just RS-232
inputs and outputs) require this protection during man-
ufacturing. Therefore, the Machine Model is less rele-
vant to the I/O ports than are the Human Body Model
and IEC1000-4-2.
±15kV ESD-Protected, EMC-Compliant,
230kbps, 3-Tx/3-Rx RS-232 IC
6 _______________________________________________________________________________________
Figure 2. Human Body ESD Test Model and ESD-Generator
Current Waveform
Figure 3. IEC1000-4-2 Test Model and ESD-Generator Current
Waveform
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
100pF
R
C
1M R
D
1500
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
C
s
150pF
R
C
50M to 100M R
D
330
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
a)
a)
b)b)