Isolated RS-485
NVE offers a broad line of single-chip isolated RS-485 transceivers.
IsoLoop logic isolators can also be used as part of multi-chip designs to isolate
signals using particular non-isolated transceivers.
Illustrative circuits:
Recommended application bulletins:
RS-485 single-chip transceiver selector guide
Single-Chip
RS-485/PROFIBUS Isolated Transceivers
NVEs single-chip
isolated RS-485 transceivers include digital- and passive-input versions,
fractional-load versions, and PROFIBUS-compliant versions. Termination resistors
can be added to maximize speed and transmission length. Fail-safe resistors guarantee
a known state on a terminated bus with no active transceivers. NVE transceivers
are available with data rates are up to 40 Mbps. Parts are available in 0.3"
and 0.15" 16-pin SOIC packages.
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Single-Chip
Passive-Input RS-485 Isolated Transceivers
NVEs unique passive-input
isolated transceivers have current-mode inputs for maximum flexibility. A
typical circuit is shown above.
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Single-Component
RS-485 Receiver Using IL610
An IL610 can be used as a simple isolated RS-485 receiver. No external
resistors are required, and cabling is greatly simplified by eliminating the
need to power the input side of the receiving board. The circuit is failsafe
because the IL610 is guaranteed to switch to the high state when the coil
input current is less than 500 µA. No current-limiting resistor
is needed for a single receiver because it will draw less current than the
driver maximum. There is also no need for line termination resistors in most
IL610 line receiver applications below a data rate of about 10 Mbps because
the IL610 coil resistance of approximately 70 Ohms is close to the characteristic
impedance of most cables.
The IL610 provides 2.5 kVrms isolation (one minute), and 20 kV/µs
transient immunity. The IL610-1 is a unique MSOP isolator for space-critical
boards.
For more information on using IL600-Series Isolators as differential receivers,
see Application Bulletin No. 10 (.pdf).
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RS-485
Repeater Using IL610
Simple, low cost, isolated repeater systems can be made with an RS-485 transceiver in drive mode and an IL610. Repeaters can
extend the useful cable length and node count indefinitely, provided the network
controller can tolerate the additional propagation delays.
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Isolated
Fractional Load RS-485 Using IL614
NVE offers a broad line of single-chip isolated RS-485 transceivers, but
the unique IL614 three-channel isolator can also be used as part of a multi-chip
design with non-isolated transceivers. The IL614 provides 2.5 kVrms isolation
(1 minute) and 20 kV/µs transient immunity. The IL614-3 is
in a narrow-body (0.15"-wide) package when board space is critical.
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Isolated
RS-485 Using IL710 and IL711
IL700 high-speed digital signal isolators can be used as part of multi-chip
designs using non-isolated RS-485 transceivers. Circuits can be configured
with three IL710s (circuit above) or one IL710 and one IL711 (circuit below).
The IL710 and IL711 provide 2.5 kVrms isolation (1 minute) and 30 kV/µs
typical common-mode transient immunity. The IL710-1 and IL711-1
are unique MSOP one- and two-channel isolators to minimize board space.

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