MAX14782E_14 Datasheet, PDF (15/17 Pages) Maxim Integrated Products – 500Kbps 3.3V to 5V RS-485/RS-422 Transceiver with ±35kV HBM ESD Protection

MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Figure 12 shows the IEC 61000-4-2 model, and Figure
13 shows the current waveform for IEC 61000-4-2 ESD
Contact Discharge test.
Applications Information
Driver Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus connec-
tion. The first, a current limit on the output stage provides
immediate protection against short circuits over the whole
common-mode voltage range. The second, a thermal-shut-
down circuit, forces the driver outputs into a high-imped-
ance state if the die temperature exceeds +160°C (typ).
Low-Power Shutdown Mode
Low-power shutdown mode is initiated by bringing RE
high and DE low. In shutdown, the devices draw less than
10µA of supply current.
RE and DE can be connected together and driven simul-
taneously. The MAX14782E is guaranteed not to enter
shutdown if RE is high and DE is low for less than 50ns.
If the inputs are in this state for at least 800ns (max), the
device is guaranteed to enter shutdown.
Typical Applications
The MAX14782E transceiver is designed for bidirectional
data communications on multipoint bus transmission
lines. Figure 14 shows a typical network application cir-
cuit. To minimize reflections, terminate the line at both
ends with its characteristic impedance and keep stub
lengths off the main line as short as possible.
R_C
50MΩ TO 100MΩ
R_D
330Ω
CHARGE CURRENT- DISCHARGE
LIMIT RESISTOR RESISTANCE
HIGH-
VOLTAGE
DC
SOURCE
CS
150pF
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
Figure 12. IEC 61000-4-2 ESD Test Model
I
100%
90%
10%
tR = 0.7ns TO 1ns
30ns
t
60ns
Figure 13. IED 61000-4-2 ESD Generator Current Waveform
DI
D
120Ω
B
DE
A
RO
R
RE
MAX14782E
B
A
R
D
DI
Figure 14. Typical Half-Duplex RS-485 Network
DE RO RE
120Ω
B
B
A
A
R
D
DI
DE RO RE
DE
D
DI
R
RO
RE
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