Isolated RS-422/RS-485/PROFIBUS NVE offers a broad line of single-chip isolated RS-422, RS-485, and PROFIBUS transceivers. IsoLoop logic isolators can also be used as part of multi-chip designs to isolate signals using particular non-isolated transceivers. Illustrative circuits are:				RS-485 Tips (04:03)
		Single-Chip RS-485 Isolated Transceivers
		Single-Component RS-485 Receiver Using IL610
		Single-Chip RS-422 Isolated Transceivers
		RS-422 Network with Two IL610 Receivers
		RS-485 Repeater Using IL610
		Isolated Fractional Load RS-485 Using IL614
		PROFIBUS Using IL3685 Single-Chip Transceiver
		Isolated PROFIBUS Using IL710 and IL711

		AB-5: Isolated RS-485 and RS-422 (.pdf) Dramatically reduce chip count and board area with IL400- and IL3000-Series single-chip isolated transceivers.
		AB-6: RS-485 Systems (.pdf) Practical tips and rules of thumb for making RS-485 systems work.
		AB-10: Differential Line Receivers Using IL600-Series Isolators (.pdf) The unique passive inputs of the IL600-Series Isolators are ideal for direct connection to differential networks such as RS-485 and RS-422. This document shows how to save components and reduce cost.
		AB-19: PROFIBUS Compliance: A Hardware Design Guide (.pdf) Hardware design best practices for Profibus DP nodes. Covers three important but sometimes tricky design considerations: isolation, Profibus compatibility, and bus node polarity.

Selector Guide for single-chip isolated RS-485 transceivers

Single-Chip RS-485 Isolated Transceivers

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An IL610 can be used as a simple isolated RS-485/RS-422 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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Single-Chip RS-422 Isolated Transceivers

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This circuit shows a two-receiver RS-422 network using IL610s. Two 17 Ohm current-limiting resistors prevent two IL610 coils from exceeding the maximum load of the transceiver chip. Placement of the current-limiting resistors on both lines provides better dynamic signal balance.

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Simple, low cost, isolated repeater systems can be made with an RS-422 transmitter/receiver pair (or 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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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 PROFIBUS Using IL3685 Single-Chip Transceiver

The 220 ohm termination resistor, along with another 220 ohm resistor and the other end of the bus, matches the bus impedance to minimize reflections. The 390 ohm "fail-safe" resistors guarantee a known state with no active transceivers. Bypass capacitors should be placed as close as possible to the appropriate IC.

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NVE offers the unique IL3685 single-chip isolated PROFIBUS transceiver, but IL700 high-speed digital signal isolators can also be used as part of multi-chip designs using non-isolated PROFIBUS 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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