Datasheet

±15kV ESD Protection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against ESD encoun-
tered during handling and assembly. The MAX3440E–
MAX3444E receiver inputs/driver outputs (A, B) have
extra protection against static electricity found in normal
operation. Maxim’s engineers have developed state-of-
the-art structures to protect these pins against ±15kV ESD
without damage. After an ESD event, the MAX3440E–
MAX3444E continue working without latchup.
ESD protection can be tested in several ways. The
receiver inputs are characterized for protection to
±15kV using the Human Body Model.
ESD Test Conditions
ESD performance depends on a number of conditions.
Contact Maxim for a reliability report that documents test
setup, methodology, and results.
Human Body Model
Figure 9a shows the Human Body Model, and Figure
9b 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
1.5kΩ resistor.
Driver Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or bus contention. The
first, a foldback current limit on the driver output stage,
provides immediate protection against short circuits over
the whole common-mode voltage range. The second, a
thermal shutdown circuit, forces the driver outputs into
a high-impedance state if the die temperature exceeds
+160°C. Normal operation resumes when the die tem-
perature cools to +140°C, resulting in a pulsed output
during continuous short-circuit conditions.
Figure 9b. Human Body Model Current WaveformFigure 9a. 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
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
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Maxim Integrated │ 13
MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers