MAX13430E Datasheet, PDF (16/19 Pages) Maxim Integrated Products – RS-485 Transceivers with Low-Voltage Logic Interface

RS-485 Transceivers with Low-Voltage
Logic Interface
Applications Information
256 Transceivers on the Bus
The standard RS-485 receiver input impedance is a
one-unit load (12kΩ), and the standard driver can drive
up to 32 unit loads. The MAX13430E family of trans-
ceivers has a 1/8-unit load receiver input impedance
(96kΩ), allowing up to 256 transceivers to be connect-
ed in parallel on one communication line. Any combina-
tion of these devices, as well as other RS-485
transceivers with a total of 32-unit loads or less, can be
connected to the line.
Reduced EMI and Reflections
The MAX13430E/MAX13432E feature reduced slew-
rate drivers that minimize EMI and reduce reflections
caused by improperly terminated cables, allowing
error-free data transmission up to 500kbps.
Driver Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus con-
tention. The first, a foldback current limit on the output
stage, provides immediate protection against short cir-
cuits over the whole common-mode voltage range (see
the Typical Operating Characteristics.) The second, a
thermal-shutdown circuit, forces the driver outputs into
a high-impedance state if the die temperature exceeds
+150°C (typ).
Typical Applications
The MAX13430E/MAX13433E transceivers are
designed for bidirectional data communications on mul-
tipoint bus transmission lines. Figures 12 and 13 show
typical network applications circuits. To minimize reflec-
tions, terminate the line at both ends with its character-
istic impedance, and keep stub lengths off the main
line as short as possible. The slew-rate-limited
MAX13430E/MAX13432E allow the RS-485 network to
be more tolerant of imperfect termination.
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