MAX3440E Maxim, MAX3440E Datasheet - Page 13

• Manufacturer Part Number: MAX3440E
• Description: 15kV ESD-Protected / 60V Fault-Protected / 10Mbps / Fail-Safe RS-485/J1708 Transceivers
• Manufacturer: Maxim

As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against ESD
encountered 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 performance depends on a number of conditions.
Contact Maxim for a reliability report that documents
test setup, methodology, and results.
Figure 9a. Human Body ESD Test Model
VOLTAGE
SOURCE
HIGH-
10Mbps, Fail-Safe RS-485/J1708 Transceivers
DC
±15kV ESD-Protected, ±60V Fault-Protected,
CHARGE-CURRENT-
LIMIT RESISTOR
1M
R
C
100pF
9
______________________________________________________________________________________
C s
STORAGE
CAPACITOR
1.5k
RESISTANCE
DISCHARGE
±15kV ESD Protection
R
D
9
ESD Test Conditions
DEVICE
UNDER
TEST
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.
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 cir-
cuits over the whole common-mode voltage range. The
second, a thermal shutdown circuit, forces the driver out-
puts into a high-impedance state if the die temperature
exceeds +160°C. Normal operation resumes when the
die temperature cools to +140°C, resulting in a pulsed
output during continuous short-circuit conditions.
Figure 9b. Human Body Model Current Waveform
AMPERES
I
P
36.8%
100%
90%
10%
0
0
t
RL
Driver Output Protection
CURRENT WAVEFORM
TIME
t
DL
I r
Human Body Model
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
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