Datasheet

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-485
inputs) require this protection during manufacturing.
Therefore, the Machine Model is less relevant to the I/O
ports than are the Human Body Model.
±4kV Electrical Fast Transient/Burst Testing
(IEC 1000-4-4)
IEC 1000-4-4 Electrical Fast Transient/Burst (EFT/B) is
an immunity test for the evaluation of electrical and
electronic systems during operating conditions. The
test was adapted for evaluation of integrated circuits
with power applied. Repetitive fast transients with
severe pulsed EMI were applied to signal and control
ports. Over 15,000 distinct discharges per minute are
sent to each interface port of the IC or equipment under
test (EUT) simultaneously with a minimum test duration
time of one minute. This simulates stress due to dis-
placement current from electrical transients on AC
mains, or other telecommunication lines in close prox-
imity. Short rise times and very specific repetition rates
are essential to the validity of the test.
Stress placed on the EUT is severe. In addition to the
controlled individual discharges placed on the EUT,
extraneous noise and ringing on the transmission line
can multiply the number of discharges as well as
increase the magnitude of each discharge. All cabling
was left unterminated to simulate worst-case reflections.
The MAX3040–MAX3045 were setup as specified in
IEC 1000-4-4 and the Typical Operating Circuit of this
data sheet. The amplitude, pulse rise time, pulse dura-
tion, pulse repetition period, burst duration, and burst
period (Figure 8) of the burst generator were all verified
with a digital oscilloscope according to the specifica-
tions in IEC 1000-4-4 sections 6.1.1 and 6.1.2. A simpli-
fied diagram of the EFT/B generator is shown in Figure
7. The burst stresses were applied to Y1–Y4 and Z1–Z4
simultaneously.
IEC 1000-4-4 provides several levels of test severity
(see Table 1). The MAX3040–MAX3045 pass the 4000V
stress, a special category “X” beyond the highest level
for severe (transient) industrial environments for
telecommunication lines.
MAX3040–MAX3045
±10kV ESD-Protected, Quad 5V RS-485/RS-422
Transmitters
8 _______________________________________________________________________________________
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
C
s
100pF
R
C
1MΩ
R
D
1.5kΩ
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 6a. Human Body ESD Test Model
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
Figure 6b. Human Body Model Current Waveform
ON I/O,
SIGNAL, DATA
AND CONTROL
PORTS
EFT
LEVEL
PEAK
VOLTAGE
REPETITION
RATE (kHz)
INDUSTRIAL
ELECTRO-
MAGNETIC
ENVIROMENT
1 250 5 Well protected
2 500 5 Protected
3 1000 5
Typical
4 2000 5
Severe
X 4000 5
MAX3040–MAX3045
Table 1. Test Severity Levels for
Communication Lines