Isoloop Magnetic Couplers-by Babitha by yubenjoseph@gmail.com

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									Seminar Report – ’04                         ISOLOOP MAGNETIC COUPLERS




                          1. INTRODUCTION

       Couplers, also known as "isolators" because they electrically isolate as

well as transmit data, are widely used in industrial and factory networks,

instruments, and telecommunications. Every one knows the problems with

optocouplers. They take up a lot of space, are slow, optocouplers age and their

temperature range is quite limited. For years, optical couplers were the only

option. Over the years, most of the components used to build instrumentation

circuits have become ever smaller. Optocoupler technology, however, hasn‘t kept

up. Existing coupler technologies look like dinosaurs on modern circuit boards.


       Magnetic couplers are analogous to optocouplers in a number of ways.

Design engineers, especially in instrumentation technology, will welcome a

galvanically-isolated data coupler with integrated signal conversion in a single IC.

My report will give a detailed study about ‗ISOLOOP MAGNETIC

COUPLERS‘.




Dept. of EEE                             1                MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS




    2. INDUSTRIAL NETWORKS NEED ISOLATION


2.1 GROUND LOOPS


       When equipment using different power supplies is tied together (with a

common ground connection) there is a potential for ground loop currents to exist.

This is an induced current in the common ground line as a result of a difference in

ground potentials at each piece of equipment. Normally all grounds are not in the

same potential.


       Widespread electrical and communications networks often have nodes

with different ground domains. The potential difference between these grounds

can be AC or DC, and can contain various noise components. Grounds connected

by cable shielding or logic line ground can create a ground loop—unwanted

current flow in the cable. Ground-loop currents can degrade data signals, produce

excessive EMI, damage components, and, if the current is large enough, present a

shock hazard.


       Galvanic isolation between circuits or nodes in different ground domains

eliminates these problems, seamlessly passing signal information while isolating

ground potential differences and common-mode transients. Adding isolation

components to a circuit or network is considered good design practice and is often

mandated by industry standards. Isolation is frequently used in modems, LAN and

industrial network interfaces (e.g., network hubs, routers, and switches),

telephones, printers, fax machines, and switched-mode power supplies.

Dept. of EEE                            2                 MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS




                     3. GALVANIC COUPLERS

       Magnetic couplers are analogous to optocouplers in a number of ways.

Optocouplers transmit signals by means of light through a bulk dielectric that

provides galvanic isolation (see Figure 1).




Figure 1. Both optical (A) and magnetic isolators (B) provide galvanic isolation

between electronic input and output. Magnetic isolators transmit the signal by a

magnetic field rather than by photons.




Dept. of EEE                             3             MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS




       Magnetic couplers transmit signals via a magnetic field, rather than a

photon transmission, across a thin film dielectric that provides the galvanic

isolation. As is true of optocouplers, magnetic couplers are unidirectional and

operate down to DC. But in contrast to optocouplers, magnetic couplers offer the

high-frequency performance of an isolation transformer, covering nearly the entire

combined bandwidth of the two conventional isolation technologies.




Dept. of EEE                            4                MESCE, Kuttippuram
Seminar Report – ’04                            ISOLOOP MAGNETIC COUPLERS




4. PHYSICS OF THE GIANT MAGNETORESISTANCE


4.1 Giant Magnetoresistive (GMR):


        Large magnetic field dependent changes in resistance are possible in thin

film ferromagnet/nonmagnetic metallic multilayers. The phenomenon was first

observed in France in 1988, when changes in resistance with magnetic field of up

to 70% were seen. Compared to the small percent change in resistance observed in

anisotropic    magnetoresistance,    this       phenomenon     was   truly   ‗giant‘

magnetoresistance.


        The spin of electrons in a magnet is aligned to produce a magnetic

moment. Magnetic layers with opposing spins (magnetic moments) impede the

progress of the electrons (higher scattering) through a sandwiched conductive

layer. This arrangement causes the conductor to have a higher resistance to current

flow.


        An external magnetic field can realign all of the layers into a single

magnetic moment. When this happens, electron flow will be less effected (lower

scattering) by the uniform spins of the adjacent ferromagnetic layers. This causes

the conduction layer to have a lower resistance to current flow. Note that these

phenomenon takes places only when the conduction layer is thin enough (less than

5 nm) for the ferromagnetic layer‘s electron spins to affect the conductive layer‘s

electron‘s path.




Dept. of EEE                                5                MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS




Figure 2—In both a and b, the A layers are the nonmagnetic conductive layer and

the B layers are adjacent magnetic layers of opposing orientation. a—Layer A is

high resistance because of higher scattering of electrons flowing through it. b—An

applied magnetic field realigns the magnetic moments in the B layers, resulting in

a lower resistance in lay


       The resistance of two thin ferromagnetic layers separated by a thin

nonmagnetic conducting layer can be altered by changing the moments of the

ferromagnetic layers from parallel to antiparallel, or parallel but in the opposite

direction.


       Layers with parallel magnetic moments will have less scattering at the

interfaces, longer mean free paths, and lower resistance. Layers with antiparallel


Dept. of EEE                            6                MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS
magnetic moments will have more scattering at the interfaces, shorter mean free

paths, and higher resistance (see Figure 2 & 3).




Figure 3. In a giant magneto resistive sensor, the resistance of two thin

ferromagnetic layers separated by a thin nonmagnetic conducting layer can be

altered by changing the moments of the ferromagnetic layers from parallel to

antiparallel.


        For spin-dependent scattering to be a significant part of the total resistance,

the layers must be thinner than the mean free path of electrons in the bulk

material. For many ferromagnets the mean free path is tens of nanometers, so the

layers themselves must each be typically <10 nm (100 Å). It is therefore not

surprising that GMR was only recently observed with the development of thin

film deposition systems.


        The spin of electrons in a magnet are aligned to produce a magnetic

moment. Magnetic layers with opposing spins (magnetic moments) impede the

progress of the electrons (higher scattering) through a sandwiched conductive

Dept. of EEE                              7                 MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS
layer. This arrangement causes the conductor to have a higher resistance to current

flow.




4.2 GMR MATERIALS:


        There are presently several GMR multilayer materials used in sensors and

sensor arrays. The most commonly used material in commercial GMR sensors has

a saturation field of 300 Oe and GMR of 15%. Newer FeCo/Cu multilayer

materials with saturation fields below 100 Oe and GMR over 10 % are also used.


        The following chart shows a typical characteristic for an NVE GMR

material:




Dept. of EEE                            8                 MESCE, Kuttippuram
Seminar Report – ’04                      ISOLOOP MAGNETIC COUPLERS




                 Figure 4 : characteristics of GMR materials.




Dept. of EEE                          9                MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS




       Notice that the output characteristic is omnipolar, meaning that the

material provides the same change in resistance for a directionally positive

magnetic field as it does for a directionally negative field. This characteristic has

advantages in certain applications.


       For example, when used on a magnetic encoder wheel, a GMR sensor

using this material will provide a complete sine wave output for each pole on the

encoder thus doubling the resolution of the output signal.


       The material shown in the plot is used in most of GMR sensor products. It

provides a 98% linear output from 10% to 70% of full scale, a large GMR effect

(13% to 16%), a stable temperature coefficient (0.15%/°C) and temperature

tolerance (+150°C), and a large magnetic field range (0 to ±300 Gauss).


       For spin-dependent scattering to be a significant part of the total resistance,

the layers must be thinner than the mean free path of electrons in the bulk

material. For many ferromagnets the mean free path is tens of nanometers, so the

layers themselves must each be typically <10 nm (100 Å). It is therefore not

surprising that GMR was only recently observed with the development of thin

film deposition systems.




Dept. of EEE                             10                  MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS




    5. CONSTRUCTION OF A ISOLOOP MAGNETIC

                                  COUPLER




Figure 5. In a GMR, isolator data travels via a magnetic field through a dielectric

isolation to affect that resistance elements arranged in a bridge configuration.




Figure 6. A magnetic coupler consists of an onchip microscopic coil that generates

a magnetic field and a GMR sensor that detects that field. The current in the

planar coil produce a magnetic field. The magnetic field produced by the field coil

of the input affects the spin of electrons in the anti-ferromagnetic layers, reducing

the resistance of the bridge sensors.

Dept. of EEE                             11                MESCE, Kuttippuram
Seminar Report – ’04                         ISOLOOP MAGNETIC COUPLERS




       To put this phenomenon to work, a Wheatstone bridge configuration of

four GMR sensors (see Figure 5 & 6). The manufacturing process allows thick

film magnetic material to be deposited over the sensor elements to provide areas

of magnetic shielding or flux concentration. Various op-amp or in-amp

configurations can be used to supply signal conditioning from the bridge‘s

outputs. This forms the basis of an isolation receiver. The isolation transmitter is

simply coil circuitry deposited on a layer between the GMR sensors layers and the

thick film magnetic shielding layer (see Figure 5). Current through this coil layer

produce the magnetic field, which overcomes the antiferromagnetic layers there

by reducing the sensor‘s resistance.


5.1 SENSOR ARRAYS:


       GMR elements can be patterned to form simple resistors, half bridges,

Wheatstone bridges, and even X-Y sensors. Single resistor elements are the

smallest devices and require the fewest components, but they have poor

temperature compensation and usually require the formation of some type of


Dept. of EEE                            12                MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS
bridge by using external components. Alternatively they can be connected in

series with one differential amplifier per sensor resistor. Half bridges take up more

area on a chip but offer temperature compensation, as both resistors are at the

same temperature. Half bridges can be used as field gradient sensors if one of the

resistors is some distance from the other. They can function as field sensors if one

of the resistors is shielded from the applied field. Figure 4 shows a portion of an

array of 16 GMR halfbridge elements with 5 µm spacing. The elements are 1.5

µm wide by 6 µm high with a similar size element above the center tap. The




bottoms of the stripes are connected to a common ground connection and the tops

of the half bridges are connected to a current supply. The center taps are

connected to 16 separate pads on the die. A bias strap passes over the lower

elements to provide a magnetic field to bias the elements.




Dept. of EEE                             13                  MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS
Figure 7. Part of a 16-element array of GMR half-bridge sensors with 5 µm

spacing. The first three elements have portions removed to show the three layers

and their interconnections.


5.2 Signal Processing


       Adding signal processing electronics to the basic sensor element increases

the functionality of sensors. The large output signal of the GMR sensor element

Introduction means less circuitry, smaller signal errors, less drift, and better

temperature stability compared to sensors where more amplification is required to

create a usable output.




   For the GMR products, we add a simple comparator and output transistor

circuit to create the world‘s most precise digital magnetic sensor. For these



Dept. of EEE                           14               MESCE, Kuttippuram
Seminar Report – ’04                            ISOLOOP MAGNETIC COUPLERS
products, no amplification of the sensor‘s output signal is necessary. A block

diagram of this circuitry is shown in the figure 8.




Figure 8: a typical signal processing circuit


       The GMR Switch holds its precise magnetic operate point over extreme

variations in temperature and power supply voltage. This is a low cost method.




Dept. of EEE                             15              MESCE, Kuttippuram
Seminar Report – ’04                         ISOLOOP MAGNETIC COUPLERS




6. WORKING OF A ISOLOOP MAGNETIC COUPLER

       In the Isoloop magnetic couplers, a signal at the input induces a current in

a planar coil (see figure no: 5).The current produces a magnetic field, which is

proportional to the current in the planar coil. The resulting magnetic field

produces a resistance change in the GMR material, which is separated from the

planar coil by a high voltage insulating material. Since the GMR is sensitive

parallel to the plane of the substrate, this allows a considerably more compact

construction than would be possible with Hall sensors. The resistance change in

GMR material, which was caused by the magnetic field, is amplified by an

electronic circuit and impressed upon the output as a reproduction of the input

signal. Since changes in the ground potential at the input, output or both doesn‘t

produce a current in the planar coil, no magnetic field is created. The GMR

material doesn‘t change. In this way safe galvanic signal isolation is achieved and

at the same time a corresponding common mode voltage tolerance.




Dept. of EEE                            16                MESCE, Kuttippuram
Seminar Report – ’04                         ISOLOOP MAGNETIC COUPLERS




      7. ADVANTAGES OF MAGNETIC COUPLING

       The advantages of magnetic coupling include high bandwidth, small

footprint, excellent noise immunity, and temperature stability.



7.1 Bandwidth:

       IsoLoop couplers are 5–10 times faster than the fastest optocouplers, and

have correspondingly faster rise, fall, and propagation times (see Figure 9).

Shorter rise and fall times also reduce power consumption in the device and

system by minimizing time in active regions.




Dept. of EEE                            17                MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS




Figure 9. Magnetic couplers (blue trace) have faster rise, fall, and propagation

times than the fastest optocouplers (yellow trace) for the same input (purple trace).




7.2 Small Footprint:


       IsoLoop couplers can be fabricated in <1 mm2 of die area per channel (see

Figure 10), allowing multichannel devices in SSOP packages. Less board real

estate means both more room for other functions and lower prices. Furthermore,




Dept. of EEE                             18                MESCE, Kuttippuram
Seminar Report – ’04                      ISOLOOP MAGNETIC COUPLERS
because of their small die size, IsoLoop couplers cost no more than high-

performance optocouplers.




Figure 10. The four-channel magnetic coupler die in the photomicrograph has a

footprint of only 2.1 mm2.




7.3 Noise Immunity:

Dept. of EEE                         19              MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS
       Magnetic couplers provide transient immunity up to 25 kV/µs, compared

to 10 kV/µs for optocouplers. Transient immunity is especially important in harsh

industrial and process control environments.


7.4 Temperature Stability:


       Because the transmission and sensing elements are not subject to

semiconductor temperature variations, magnetic couplers operate to 100°C and

above; for most optocouplers the upper limit is 75°C. Magnetic couplers are also

immune to optocouplers‘ inherent performance decay with age.




Dept. of EEE                           20               MESCE, Kuttippuram
Seminar Report – ’04                         ISOLOOP MAGNETIC COUPLERS




                       8. DIGITAL ISOLATORS

       High-speed digital isolators are CMOS devices created by integrating

active circuitry and GMR-based IsoLoop technology. These devices offer true

isolated logic integration in a level not previously available. All transmit and

receive channels operate at 110 Mbd over the full temperature and supply voltage

range. The symmetric magnetic coupling barrier provides a typical propagation

delay of only 10 ns and a pulse width distortion of 2 ns achieving the best

specifications of any isolator device. Typical transient immunity of 30 kV/µs is

unsurpassed.


8.1 Dynamic Power Consumption:


       Isoloop devices achieve their low power consumption from the manner by

which they transmit data across the isolation barrier. By detecting the edge

transitions of the input logic signal and converting these to narrow current pulses,

a magnetic field is created around the GMR Wheatstone bridge. Depending on the

direction of the magnetic field, the bridge causes the output comparator to switch

following the input logic signal. Power consumption is independent of mark-to-

space ratio and solely dependent on frequency. This has obvious advantages over

optocouplers whose power consumption is heavily dependent on its on-state and

frequency. The maximum power supply current per channel for IsoLoop is:




Dept. of EEE                            21                MESCE, Kuttippuram
Seminar Report – ’04                           ISOLOOP MAGNETIC COUPLERS

8.2 Data Transmission Rates:


       The reliability of a transmission system is directly related to the accuracy

and quality of the transmitted digital information. For a digital system, those

parameters, which determine the limits of the data transmission, are pulse width

distortion and propagation, delay skew.


       Propagation delay is the time taken for the signal to travel through the

device. This is usually different when sending a low-to-high than when sending a

high-to-low signal. This difference, or error, is called pulse width distortion

(PWD) and is usually in ns. It may also be expressed as a percentage:


       PWD% = (Maximum Pulse Width Distortion (ns) /Signal Pulse

       Width (ns)) x 100%


For example: For data rates of 12.5 Mb


    PWD% = (3 ns/80 ns) x 100% = 3.75%


       This figure is almost three times better than for any available Optocoupler

with the same temperature range, and two times better than any optocoupler

regardless of published temperature range. The IsoLoop range of isolators

surpasses the 10% maximum PWD recommended by PROFIBUS, and will run at

almost 35 Mb before reaching the 10% limit.




Dept. of EEE                              22             MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS
       Propagation delay skew is the difference in time taken for two or more

channels to propagate their signals. This becomes significant when clocking is




       involved since it is undesirable for the clock pulse to arrive before the data

has settled. A short propagation delay skew is therefore critical, especially in high

data rate parallel systems, to establish and maintain accuracy and repeatability.

The IsoLoop range of isolators all has a maximum propagation delay skew of 6 ns,

which is five times better than any optocoupler. The maximum channel to channel

skew in the IsoLoop coupler is only 3 ns, which is ten times better than any

optocoupler.




Dept. of EEE                             23                MESCE, Kuttippuram
Seminar Report – ’04                         ISOLOOP MAGNETIC COUPLERS




  9. COMPARISON BETWEEN OPTOCOUPLER AND

                 ISOLOOP MAGNETIC COUPLER

       Unlike typical microsecond TON/TOFF times of optoisolators, IsoLoop-

isolators are typically 1 ns, which is more than 1000 times faster than its light-

based rival. The IsoLoop-isolators also have identical TON/TOFF times, which

produce no pulse-width distortion as is the case with many optoisolators having

differing TON/TOFF times. Propagation delays are less than 10 ns with inter-

channel skewing of less than 2 ns. Isoloop-isolators have up to four channels per

package in a variety of device direction configurations. These standard devices are

great for bus isolation, serial ADCs and DACs, and communication isolation. The

working range of optocouplers is only between zero and ten megahertz. The

IsoLoop couplers have data transmission speeds up to100 mega baud. IsoLoop

devices will operate over a wide temperature range of -40 to +100C, compared

with the restricted range of 0 to +70C for optoisolators. The power consumption

of IsoLoop devices is independent of the mark space ratio and solely dependent on

frequency. This makes for lower power consumption than optoisolators, whose

power consumption is heavily dependent on state and frequency. With data rates

up to 100Mbaud, the IsoLoop technology offers rates of up to ten times that of

optoisolators.




Dept. of EEE                            24                MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS




                  10. CURRENT APPLICATIONS

       Magnetic isolators are quickly finding their way into process control and

industrial applications. Isolation of A/D interfaces is one popular use. In addition,

magnetic isolators‘ combination of speed and packaging density provides a good

method of efficient data channel management when multiple A/Ds need to be

interfaced on the same circuit card. A four-channel part with three channels going

one way and one going the other is available for A/D interface applications.

Magnetic couplers also enable higher speed factory networks such as Profibus and

other protocols. These devices are great for bus isolation, serial ADCs and DACs,

and communication isolation. The combination of the fast and high-density

IsoLoop couplers with high packing density allows efficient data channel

management where several A/D channels must be isolated on a board.




Dept. of EEE                             25                MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS




10.1 Digital Isolation Applications:


      ADCs and DACs

      Digital Field bus

      RS485 and RS422

      Multiplexed Data Transmission

      Data Interfaces

      Board-To-Board Communication

      Digital Noise Reduction

      Operator Interface

      Ground Loop Elimination

      Peripheral Interfaces

      Serial Communication

      Logic Level Shifting




Dept. of EEE                           26           MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS




                           11. THE FUTURE

       Magnetic field detection has vastly expanded as industry has used a variety

of magnetic sensors to detect the presence, strength, or direction of magnetic

fields from the Earth, permanent magnets, magnetized soft magnets, and the

magnetic fields associated with current. These sensors are used as proximity

sensors, speed and distance measuring devices, navigation compasses, and current

sensors. They can measure these properties without actual contact to the medium

being measured and have become the eyes of many control systems.




Dept. of EEE                           27                MESCE, Kuttippuram
Seminar Report – ’04                         ISOLOOP MAGNETIC COUPLERS




                              12. SUMMARY

       Magnetic couplers will in time be even faster and have more channels.

More types of integrated bus transceivers will be available. Several manufacturers

are planning to introduce magnetic couplers. The U.S. military is providing

significant funding for advanced magnetic coupler development because of the

value of their high speed and noise immunity in aircraft and other systems.


       Speeds, currently limited by the silicon electronics and not the coil/GMR

structure, are expected to increase as ICs scale down and become faster. It has

reported prototype devices with speeds of 300 Mbaud and switching times of <1

Dept. of EEE                            28                MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS
ns. Also under development are higher-density parts (full byte-wide couplers) and

more functionality (latching bus transceivers). Finally, the inherent linearity of a

resistive coil and resistive sensing elements make magnetic couplers well suited

for linear data protocols such as low-voltage differential signaling.




Dept. of EEE                             29                MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS




                           13. REFERENCES

   1.   J.Daughton and Y. Chen. "GMR Materials for Low Field Applications,"

        IEEE Trans Magn, Vol. 29:2705-2710, 2003.pp.18-21

   2.   Michael J. Caruso, Tamara Bratland, C. H. Smith, and Robert Schneider,

        ―A New Perspective on Magnetic Field Sensing,‖ Sensors Magazine, vol.

        15, no. 12, (December 2002), pp. 34-46.

   3.   Carl H. Smith and Robert W. Schneider, ―Low-Field Magnetic Sensing

        with GMR Sensors, Part 1: The Theory of Solid-State Sensing,‖ Sensors

        Magazine, vol. 16, no. 9, (September 2002), pp. 76-83.

   4.   Carl H. Smith and Robert W. Schneider, ―Low-Field Magnetic Sensing

        with GMR Sensors, Part 2: GMR Sensors and their Applications,‖

        Sensors Magazine, vol. 16, no. 10, (October 2002), pp. 84- 91.


WEB SITES


   1. http://www.circuitcellar.com/library/print/0502/JEFF/4.asp

   2. http://www.sensorsmag.com/

   3. http://www.nve.com/isoloop/news/hispdnr.php

   4. http://www.electronicstalk.com/news/rho/rho000.html




Dept. of EEE                           30                MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS




                            LIST OF FIGURES


  FIGURES                                                       PAGE NO


Figure 1: Both optical (A) and magnetic isolators (B).             :3


Figure 2: Giant Magnetoresistive.                                  :6


Figure 3: In a giant magneto resistive sensor.                     :7


Figure 4: Characteristics of GMR materials.                        :8


Figure 5: In a GMR.                                                : 10


Figure 6: A magnetic coupler.                                      : 10


Figure 7: 16-element array GMR half-bridge sensor.                 : 12


Figure 8: A typical signal processing circuit.                     : 13


Figure 9: Magnetic couplers Vs optocouplers


for the same input.                                                : 15


Figure 10: The four-channel magnetic coupler.                      : 16




Dept. of EEE                             31              MESCE, Kuttippuram
Seminar Report – ’04                         ISOLOOP MAGNETIC COUPLERS




                       TABLE OF CONTENTS


1. Introduction                                             :1


2. Industrial Networks Need Isolation                       :2


       2.1 Ground Loops                                     :2


3. Galvanic Couplers                                        :3


4. Physics Of The Giant Magneto resistance                  :5


       4.1 Giant Magnetoresistive (GMR)                     :5


       4.2 GMR Materials                                    :8


5. Construction Of A Isoloop Magnetic Coupler               : 10


       5.1 Sensor Arrays                                    : 11


      5.2 Signal Processing                                 : 12


6. Working Of A Isoloop Magnetic Coupler                    : 14


7. Advantages Of Magnetic Coupling                          : 15


       7.1 Bandwidth                                        : 15


       7.2 Small Footprint                                  : 16




Dept. of EEE                            32           MESCE, Kuttippuram
Seminar Report – ’04                          ISOLOOP MAGNETIC COUPLERS




        7.3 Noise Immunity                                   : 16


        7.4 Temperature Stability                            : 17


8. Digital Isolators                                         : 18


        8.1 Dynamic Power Consumption                        : 18


        8.2 Data Transmission Rates                          : 19


9. Comparison Between Optocoupler And


  Isoloop Magnetic Coupler                                   : 21


10. Current Applications                                     : 22


        10.1 Digital Isolation Applications                  : 22


11. The Future                                               : 24


12. Summary                                                  : 25


13. References                                               : 26


14. List Of Figures                                          : 27




Dept. of EEE                            33            MESCE, Kuttippuram
Seminar Report – ’04                        ISOLOOP MAGNETIC COUPLERS




                               ABSTRACT

       A new generation of couplers conquers noise with high speed and multiple

channels.


       Sensing is only half the battle in industrial control systems. Getting the

sensor data where they need to go is the other half. The data path can be strewn

with ground loops, noise, temperature extremes, and speed bottlenecks. For years,

optical couplers were the only option. Although revolutionary when they arrived

on the scene a generation ago, optocouplers have failed to keep pace with

advances in industrial networks and sensor technology, leaving many designers

frustrated by their bulk, slow speed, high power consumption, and limited

temperature range. But in the past year, the introduction of a new generation of

solid-state couplers—magnetic couplers—has been overcoming many of these

limitations.




Dept. of EEE                           34               MESCE, Kuttippuram
Seminar Report – ’04        ISOLOOP MAGNETIC COUPLERS




Dept. of EEE           35           MESCE, Kuttippuram

								
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