FAQ: Isolation, i Coupler® Technology, and i Coupler Products
Isolation
What is isolation? Why is it needed?
What are common applications that u isolation?
How is isolation specified?
What is isolation rating?
What are working voltage and rated mains voltage?
肠粉的米浆是怎么调的What is the relationship between working voltage and isolation rating?
What is the difference between basic and double (or reinforced) insulation levels?
What are transient immunity and common-mode rejection?
What other parameters are important when considering an isolation device?
Regulatory Standards
What regulatory standards address isolation products?
Traditional Isolation Technologies
What types of technologies have been ud to provide isolation?
What are optocouplers? What is optical isolation?
What is transformer isolation?
What is capacitive isolation?
i Coupler Technology
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What is i Coupler technology?
What are the benefits of i Coupler technology?
How much isolation can i Coupler products provide?
With which regulatory standards do i Coupler products comply?
飞天凤凰Do i Coupler products have VDE certification for reinforced insulation?
Are i Coupler products nsitive to external magnetic fields?
i Coupler Products
What are the different types of i Coupler products?
Which i Coupler product is best for my application?
What communications protocols are supported by i Coupler products?
What are some of the distinguishing features of the i Coupler products?
Can I replace an optocoupler with an i Coupler product in an existing design?
How do i Coupler products differ from interface products?
Does Analog Devices provide other products that employ i Coupler technology?
Are i Coupler products Pb-free?
How do I learn about new i Coupler products?
iso Power™
What is iso Power
What are common applications of iso Power?
How does iso Power work?
What are the benefits of iso Power?
How much power do iso Power products supply?
What iso Power products are currently in production?
Support
Where can I find support for designing with ADI's i Coupler products?
I did not purcha i Coupler products from Analog Devices or an authorized distributor — how can I get support?
What do the i Coupler product datasheets guarantee?
What tools or models exist to support my design?
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Isolation
What is isolation? Why is it needed?
Isolation is a means of preventing current from flowing between two communicating points. Typically, isolation is ud in two general situations. The first is where there is the potential for current surges that may damage equipment or harm humans. The cond is where interconnections involve different ground potentials and disruptive ground loops are to be avoided. In both cas, isolation is ud to prevent current flow yet allow for data or power flow between the two points.
What are common applications that u isolation?
Isolation is commonly found in applications involving high voltage, high-speed/high-precision communications, or communication over large distances. Common examples of such applications include:
q Industrial I/O systems
q Sensor interfaces
q Power supply/regulation systems
q Motor control/drive systems
q Instrumentation
The applications can be found in a wide range of markets, including:
q Medical equipment
q Communication networks
q Plasma display panels
q Hybrid automotive vehicles
How is isolation specified?
The isolation characteristics of an isolator are specified in a variety of manners, including:
q Isolation rating
q Working voltage (or rated mains voltage)
q Transient immunity (common-mode rejection)
The degree to which an isolator successfully insulates one side of an isolation barrier from high voltages on the other side is commonly described by the isolator's isolation rating and by its maximum working voltage (or rated mains voltage). In addition, the degree to which an isolator continues to correctly transfer a signal across an isolation barrier in the prence of a common-mode transient is described by its transient immunity (or common-mode rejection). Each of the three parameters is described below.
What is isolation rating?
An isolator's isolation rating (also called the test voltag e) is a measure of the protection provided against short-duration, common-mode voltage differences. Usually specified in terms of a 60 Hz RMS value, it is a rating of how much voltage can be safely applied between the input and output terminals of the device for a duration of one minute. A common isolation rating
found on isolation devices is 2.5KV RMS. Other devices have ratings such as 3.75KV RMS or higher. The isolation rating does not describe how much voltage can be safely applied across the part on an long-term continuous basis – this is described by the "working voltage" or "rated mains voltage."
What are working voltage and rated mains voltage?
The working voltage or rated mains voltage defines the maximum steady-state voltage that a part can support on a long-term continuous basis. Typical values range from 100 to 600V RMS.
What is the relationship between working voltage and isolation rating?
The relationship between a given working voltage and the required test voltage is complex and is a function of the application, the magnitude of common-mode voltage transients (Installation Category),
the "cleanliness" of the environment (Pollution Degree), and the required insulation type (Insulation Level). As a reprentative example bad on IEC 1010-1 (international standard for measurement and control equipment), a measurement and control application involving installation category II, a pollution degree of 2, basic insulation, and a working voltage of 300 V RMS has a required test voltage of 1.35KV RMS. This means that for an isolation component to be suitable for this application, it must support steady-state common-mode voltages differences of at least 300 V RMS and transient common-mode voltages differences of at least 1.35KV RMS. The relationship between working voltage and isolation rating is defined by the specific safety standard for the end-equipment under consideration.
健康饮食英语作文What is the difference between basic and double (or reinforced) insulation levels?
In general, protection against electric shock may be provided by adequate clearance (a physical spacing from the live part) or by one of two insulation levels. The insulation levels are basic insulation and double (or reinforced) insulation. The required insulation level is determined by the voltage levels involved as well as the prence or abnce of a connection from accessible parts to earth ground. In general, compared to an isolator providing basic insulation, an isolator providing double or reinforced insulation has greater requirements on its test voltage as well as on its input-to-
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output spacing. The required insulation level is defined by the specific safety standard for the end-equipment under consideration.
What are transient immunity and common-mode rejection?
An isolator's transient immunity specifies how fast of a common-mode transient between input and output a part can be subjected to while maintaining correct signal transmission. Many isolators have no specification on this parameter while others have values ranging from 5 to 25 KV/µs. All i Coupler products have a transient immunity specification of at least 25 KV/µs.
What other parameters are important when considering an isolation device?
The ideal isolator consumes no power, impos no signal errors, and supports any type of input signal. As a result, the important performance metrics are as follows:
q Required supply current, input signal current, or input drive current
q Propagation delay through the part
q Pul width distortion: the degree to which the output pul width of a signal varies from the input pul width
q Data rate: the maximum signal data rate that the part can support
q Supply and signal voltage range: the range of voltages that the part can support
q Operating temperature: the range of temperatures that the part can support
Which of the above metrics are important to a particular ur is a function of the application in question. Often in a specific application, certain parameters are important and others are not.
Other performance characteristics important to urs are an isolator's power-up/down characteristics, its performance in the prence of input noi, and its performance in the prence of a DC input or after a loss of power. In all cas, the output of an isolator should properly reflect the correct input state.
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Regulatory Standards
What regulatory standards address isolation products?
There are a wide variety of safety standards related to isolation at both the system and component levels, for various geographic regions, and for various applications. Shown below is a table summarizing commonly-ud standards for the U.S., Europe, and International geographic regions.
Table 1. Application-Level Standards.
Industrial UL 508EN 50178IEC 604
Information Technology UL 1950EN 60950IEC 950
Medical UL 2601-1EN 60601IEC 601 Measurement and Control UL 3111EN 61010-1IEC 1010-1
Telecom UL 1459EN 60950IEC 950
Houhold UL 8730-1EN 60065IEC 65
Table 2. Component-Level Standards.
Isolator UL 1577Component Acceptance
Notice #5
DIN EN60747-5-2
DIN V VDE V 0884-10
IEC 747-5
The standards that apply directly to isolation components are tho of Table 2. The standards of Table 1 apply to applications that u isolation components. The designer of such an application must assure that the appropriate isolation component is lected such that compliance with the relevant application-level standard is ensured. However, the application-level standard is not directly applicable to the isolation component. Only the standards of Table 2 are impod directly at the component level.
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Traditional Isolation Techniques
What types of technologies have been ud to provide isolation?
There are three common isolation technologies:
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q Optical
q Transformer
q Capactitive
Each has benefits and disadvantages related to price, performance, reliability, size, features and functionality. Historically, optocoupler and transformer technologies have been the most commonly ud methods.
What are optocouplers? What is optical isolation?
美国移民政策要求Optocouplers are a form of optical isolation that employs light to transmit information across an isolation barrier. Typically, a light emitting diode (LED) transmits information to a light nsitive receiver (e.g., a transistor). Optical isolation's primary benefit is that it is widely ud and accepted as a low-cost isolation solution for transmission of slower digital signals; high-speed, digital optocouplers tend to be expensive. Optocoupler-bad methods are commonly ud in applications in which the DC state of a signal is important. Becau LEDs may wear out over time, optical isolation typically requires compensation and guardbanding to guarantee application operability over life.
What is transformer isolation?
Transformer isolation employs transformer coils to transmit information across an isolation barrier. Changes in current through the transformer winding on one side of the isolation barrier induce a corresponding current on the transformer winding on the other side of the isolation barrier. Transformer-bad methods have been commonly ud in applications involving AC signals (Ethernet, for example) that are well suited for transformer coupling. Transformer isolation has advantages in systems with high data rates, and it can also be ud to provided an isolated power supply; however, transformers have typically been bulkier than alternative solutions.
i Coupler technology (e below) is a form of transformer isolation that employs micro-transformer coils to address the size and integration disadvantages of discrete transformer solutions.
What is capacitive isolation?
Capacitive isolation employs capacitors to couple data signals across an isolation barrier. This approach can offer significant performance advantages relative to optocoupler but typically suffer a high vulnerability to common-mode and ESD transients.
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i Coupler Technology
What is i Coupler technology?
i Coupler technology is a transformer-bad approach to isolation that combines the advantages of optocoupler, transformer, and miconductor technologies. By integrating micro-transformers onto miconductor dice, isolation is provided without the detrimental characteristics of the electro-optical conversions prent in optocouplers. The include excessive power consumption, large timing errors, and constraining data rate limitations. Safety agency-recognized insulation is achieved through the ud of a special insulation layer between the transformer coils. The common transformer problem of achieving DC-correctness is avoided by the u of patented "refresh" circuitry that updates the output with the correct input state in the abnce of input signal transitions.
What are the benefits of i Coupler technology?
i Coupler technology provides benefits in five key areas:
q Integration (size/cost)
q Performance
q Power consumption
q Ea-of-u
q Reliability
Integration benefits are provided by the ability to readily combine i Coupler channels with other miconductor functions or to combine multiple i Coupler channels in a common package thereby reducing size and cost relative to optocoupler implementations. Performance benefits are provided in the form of incread timing accuracy, transient immunity, and data rates relative to optocoupler components. Power consumption benefits are provided in the form of 10-to-50 times lower power consumption as well as the accompanying reduction in thermal dissipation.
Ea-of-u benefits are provided by the elimination of many of the difficulties prented by optocoupler technology as well as the addition of new features that facilitate the u of i Coupler isolators in new designs. Optocoupler problem areas that
i Couplers eliminate include their characteristic of widely-varying current transfer ratios, their LED wear-out phenomenon and the design burdens this impos, and their need (in most optocouplers) t
o drive their input with high current to turn on the LED. Additional ea-of-u features that i Couplers provide include the ability to operate at reduced supply voltages, the ability to translate an input signal of one voltage into an output signal of a different voltage, the u of voltage-bad digital interfaces, and the ability to operate over a wide temperature range.
Lastly, reliability benefits are achieved by the elimination of the LEDs contained within optocouplers. By using only standard CMOS process technology, i Coupler devices provide the same lifetime characteristics as other standard CMOS products.
How much isolation can i Coupler products provide?
As of this writing, most i Coupler products carry an isolation rating of either 2.5KV RMS or 5.0KV RMS (the ADuM240x and
ADuM225x isolators carry an isolation rating of 5.0KV RMS). The maximum working voltage that i Coupler products support is a function of both the safety approvals a given product has as well as its insulation lifetime as evaluated by testing performed by Analog Devices in addition to that of the safety agencies.
All i Coupler products support working voltages up to 400 V RMS. The ADuM240x and ADuM225x families support higher working voltages.
The maximum working voltage supported by the ADuM240x or ADuM225x depends on the nature of the common-mode
