Datasheet

RS-485 Transceivers with Integrated
100 Ω /120 Ω Termination Resistors
MAX13450E/MAX13451E
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Detailed Description
The MAX13450E is a full-duplex, RS-485/RS-422-
compatible transceiver and the MAX13451E is a half-
duplex, RS-485/RS-422-compatible transceiver. Both
devices have an internal 100I/120I termination resistor.
The MAX13450E/MAX13451E have a V
L
supply voltage
input to support down to a +1.8V voltage logic interface.
The MAX13450E/MAX13451E feature a 1/8-unit load
receiver input impedance, allowing up to 256 transceiv-
ers on the bus. All line interface pins are protected to
Q30kV ESD based on the HBM. These devices also
include fail-safe circuitry, guaranteeing a defined logic-
level receiver output when the receiver inputs are open
or shorted.
The MAX13450E/MAX13451E allow slew-rate-limited
driver outputs for lower data rates below 500kbps. The
SRL reduces the slew rate, which reduces EMI emissions
and reflections caused by improperly terminated cables.
The MAX13451E has a FAULT output that indicates a
fault condition on the driver. The MAX13451E also has an
INV input that inverts the phase of A and B pins.
Termination Resistor
The MAX13450E/MAX13451E feature a selectable inter-
nal termination resistor. Drive the TERM input low to
enable the internal termination resistor. Drive the TERM
input high to disable the internal termination resistor.
Drive the TERM100 input high to select the 100I termi-
nation resistor. Drive TERM100 input low to select the
120I termination resistor.
INV Input (MAX13451E)
The INV input of the MAX13451E reverses the polarity
of the RO receiver output (see Table 5 and 6). If the INV
input is high then the RO output is low under fail-safe
receiver conditions. This is the opposite polarity of nor-
mal fail-safe operations.
Fault Condition (MAX13451E)
The MAX13451E also has a FAULT output to indicate a
fault condition. The FAULT output is active high when
there is a short circuit at the driver’s output, an over/
undervoltage at the driver’s outputs, or the device’s tem-
perature is higher than +150NC.
Table 6. INV Input Function Table for
Receiver (MAX13451E)
Function Tables
(continued)
Functional Diagram (MAX13450E)
MAX13450E
D
LOGIC-LEVEL
TRANSLATION
SRL
DI
DE
TERM
Z
Y
A
B
RE
RO
TERM100
GND
V
L
V
CC
INPUT OUTPUT
RE
INV A-B RO
High X X High-Z
Low
Low
R -50mV or
Short or Open
High
P -200mV
Low
High
R -50mV or
Open
Low
P -200mV
High