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Illustrative IsoLoop Isolator Applications
Improve reliability with excellent transient immunity and magnetic immunity, and unlimited life with no degradation. Up to 6 kVrms isolation and 1 kVrms working voltage. Reduce board space with up to two channels per MSOP and up to five channels in QSOPs. Popular IsoLoop Isolator applications include PLCs, RS-485, PROFIBUS, CAN, I²C, SPI, high-fidelity audio, and power interfaces.

PLCs

 
RS-422/RS-485/PROFIBUS




RS-422 Network with Two IL610 Receivers

RS-485 Repeater Using IL610



 
Controller Area Network (CAN) Bus
Other Serial Interfaces


Isolated RS-232 Using IL712s



 
Isolated ADCs, DACs and Serial Peripheral Interface (SPI)


Multi-Channel Isolated Sampling A/D Converter Using IL261



Isolated 12-Bit DAC Using Three IL515s

Isolated Audio DAC Using Two IL260s
 
High-Fidelity Audio


Isolated Audio DAC Using Two IL260s
 
Power Interfaces

Switch-Mode Power Supply Gate Driver with an IL711 Isolator

Intelligent DC-DC Converter With Synchronous Rectification





IL600-Series Isolators for True Channel-to-Channel Isolation


In addition to 2,500 Vrms input-to-output withstand voltage, the IL600 series of IsoLoop isolators provide outstanding isolation of 400 Vrms between adjacent channels. These unique devices allow very simple channel separation in industrial process control applications, especially PLCs, where the reference ground of each channel may be different. The data line is powered by the signal, so no input power supply is required. With two channels available in the tiny MSOP footprint, more functionality can be crammed into a smaller space without sacrificing channel-to-channel or ground-to-ground isolation.

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Single-Chip RS-485 Isolated Transceivers


NVE offers the industry's broadest line of single-chip isolated RS-485 transceivers, including 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.

IsoLoop logic isolators can also be used as part of multi-chip designs to isolate signals using particular non-isolated transceivers (see examples below).

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Single-Component RS-485 Receiver Using IL610

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

RS-422 Circuit

NVE’s single-chip isolated RS-422 transceivers include digital- and passive-input versions, and fractional-load 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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RS-422 Network with Two IL610 Receivers

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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RS-485 Repeater Using IL610

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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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 PROFIBUS Using IL3685 Single-Chip Transceiver

PROFIBUS Circuit


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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Isolated PROFIBUS Using IL710 and IL711

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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Single-Chip Isolated CAN Transceiver

Isolated CAN with IL41050

The L41050 single-chip isolated CAN transceiver provides an isolated CAN interface in a single chip. Designed for harsh CAN and DeviceNet environments, the transceivers have a -55 to +125°C operating range, transmit data dominant time-out, bus pin transient protection, thermal shutdown protection, short-circuit protection, 2,500 volt isolation, and typical transient immunity of 30 kilovolts per microsecond. Unique edge-triggered inputs improve noise performance.

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Isolating Standard CAN Transceivers

Isolated CAN with IL712 Isolator

This simple circuit works with any CAN transceiver with a TxD dominant timeout, which includes all of the current-generation transceivers including the ubiquitous Philips/NXP TJA1050. Propagation delay is critical for CANbus, and the IL712 and IL721 bidirectional isolators have best-in-class propagation delay of 10 ns typical. This minimizes CAN loop delay and maximizes data rate over any given bus length, making IsoLoop Isolators ideal for CAN isolation. NVE also offers the smallest two-channel isolator, the IL712-1, in a unique MSOP-8.

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Isolating Legacy CAN Transceivers

Isolating legacy CAN transceivers

Power-on reset circuitry allows an IL712 to isolate legacy transceivers that lack TxD integrated TxD timeout, such as the Philips/NXP PCA82C250.

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Differential Signal Isolation Using an IL611

IL600-Series Isolators are ideal for isolating differential signals because you have access to the input coils and do not need input power to drive the signal across the barrier. When the voltage at node Y is greater than the voltage at node Z there is a logic high at the OUT+ node and a low on the OUT- node. Outputs are reversed when the voltage at node Z is higher than the voltage at node Y. Current-limiting resistors can be selected to ensure input coil currents are at least 5 mA and no more than 10 mA.

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Isolated RS-232 Using IL712s

IL712s provide 2.5 kVrms isolation (1 minute) and 30 kV/µs typical common-mode transient immunity. The IL712-1 is a unique MSOP dual-channel isolator to minimize board space.

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Isolated I²C Using IL612A

This circuit provides bidirectional isolation of IC bus signals with no restrictions on data rate and none of the IC bus latch-up problems common with other isolation circuits. The SCL section is similar as shown in the schematic using the other half of the P82B96.

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Isolated USB Using IL710s

In this illustrative circuit, power is supplied by USB bus power on one side of the isolation barrier, and the USB node’s external supply on the other side of the barrier. IL700-Series Isolators are specified at just 3 ns worst-case pulse width distortion. The IL700s provide 2.5 kVrms isolation (1 minute) and 30 kV/µs typical common-mode transient immunity.

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Isolated I²S Using IL710/IL711

Isolating a CD transport DAC with an isolated Inter-IC Sound (I²S) bus eliminates ground loops. The IL700-Series isolators' precision edge placement (just 100 ps jitter) all but eliminates noise-induced phase error and hum in the analog side of the audio system.

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Single-Channel Isolated SPI Delta-Sigma A/D Converter Using IL717

This circuit illustrates a typical single-channel delta-sigma isolated ADC SPI interface. The ADC is located on the bridge with no signal conditioning electronics between the bridge sensor and the ADC. The IL717 isolates the control bus from the microcontroller and the system clock is located on the isolated side of the system.

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Multi-Channel Isolated Sampling A/D Converter Using IL261

The IL261 is ideal for isolating multi-channel sampling ADCs. Isolated channels A0 and A1 control the analog channel being sampled, while the three remaining I/O lines on the IL261 isolate the SPI interface.

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Multi-Channel Isolated SPI Delta-Sigma A/D Converter Using IL261s

This circuit illustrates multiple ADCs configured in a channel-to-channel isolation configuration. The problem for designers is how to control clock jitter and edge placement accuracy of the system clock for each ADC. The best solution is to use a single clock on the system side and distribute this to each ADC. The IL261 adds a fifth channel to the IL717. This fifth channel is used to distribute a single, isolated SPI clock to multiple ADCs.

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Isolated Multi-Channel SPI A/D Sampling With IL262s

A multi-channel sampling system with separate A/D cells. The IL262 is used to control the SPI lines and send back ADC BUSY commands to the host, allowing efficient interrupt-driven sampling. The BUSY line may also be used as a frame synchronization signal in video applications.

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Isolated 12-Bit DAC Using Three IL515s

The IL515 four-channel isolator is ideally suited for parallel bus isolation. The circuit above uses three IL515s to isolate a 12-bit DAC. The unique SYNC function allows the internal clock to be shut off, eliminating the small amount of noise associated with this clock. A reset pulse is applied at power-on to ensure correct data on the isolator outputs. After the reset pulse goes high, data transfer from input to output is initiated by the leading edge of each changing data bit.

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Isolated Audio DAC Using Two IL260s

Isolation ensures the best DAC performance by eliminating much of the digital noise that tends to find its way onto the analog output. The unique five-channel IL260 isolator series allows ten channels of isolation with just two narrow-body or wide-body ICs.

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Intelligent DC-DC Converter With Synchronous Rectification

A typical primary-side controller uses a IL511, IL611, or IL711 isolator to drive the synchronous rectification signals from primary side to secondary side. IsoLoop pulse-width distortion as low as 0.3 ns typical minimizes MOSFET dead time and maximizes system efficiency. Ultra-small isolator packages (including two-channel MSOP-8s), allow the designer to squeeze more into less board area.

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Switch-Mode Power Supply Gate Driver with an IL711 Isolator

An IL711 isolates the PWM Controller from the MOS gate driver for synchronous rectification. IsoLoop pulse-width distortion as low as 0.3 ns and 100 ps jitter improves precision, minimizes MOSFET dead time and maximizes system efficiency. The IL711V-1E provides two-channels and full 2.5 kV isolation in an ultraminiature MSOP-8 package, allow the designer to squeeze more into less board area. The wide-body IL711VE provides 5 kV isolation and best-in-class 1 kV Working Voltage in a true 8 mm creepage package.

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Isolated Power Control Using IL610s

The fail-safe output (logic high output for zero coil current) of IL600 Isolators ensures the power FETs will be off on power-up. The IL600 inputs can be configured for inverting or non-inverting operation (see IL600 Product Data Sheet). The IL600 Isolators provide 2.5 kVrms isolation (1 minute), and 20 kV/µs transient immunity.

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Isolated 120 V AC Line Monitor Using IL610A

The wide input voltage range of IL600 Isolators allow connection to line voltage through current-limiting resistors. In this illustrative circuit, "Monitor Out" goes low when line voltage exceeds approximately 100 V, and high when line voltage drops below approximately 10 V. This circuit provides 2.5 kVrms isolation and 20 kV/µs transient immunity.

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Multi-Channel Isolated Alarm Monitor Using IL610As

IL600A Isolators' open-drain outputs can be wire-OR connected. A very wide input voltage range is possible, and inputs can be configured for inverting or non-inverting operation (see IL600A Product Data Sheet). This illustrative circuit provides fail-safe output (logic high output for zero coil current), 2.5 kVrms isolation, and 20 kV/µs transient immunity. Typical logic output sink current is 10 mA for each isolator. Unlike optocouplers, IsoLoop Isolators do not degrade over time and have unlimited life.

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