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How IsoLoop Isolators Work

  How IsoLoop Isolators Work

Optocouplers transmit signals by light through a bulk dielectric that provides galvanic isolation:

Optocoupler Operation

The optical elements are slow, have limited life, and the bulk dielectric limits optocoupler miniaturization. IsoLoop couplers use spintronics and magnetics rather than optics to transmit data:

IsoLoop Operation

IsoLoop Isolators consist of an “IsoLoop” microscopic coil and an integrated “spin valve” made of GMR resistors:

IsoLoop Construction

A spin valve is spintronic  GMR element with two stable resistance states. The coil creates a magnetic field proportional to the input current signal across a dielectric film. The field changes the spin polarization of the spin valve resistor elements and thus their resistance The spin valve output is amplified and conditioned to produce an isolated replica of the input signal. Thus IsoLoop Isolators transmit signals by a magnetic field and electron spin rather than by light and photons.

The entire device is shielded for immunity to external fields. Ground potential variations are common to both sides of the field-producing input coil, so they do not generate a current. Therefore, no magnetic field results, and these variations are rejected, resulting in a very large common-mode rejection ratio (CMRR) and true galvanic isolation.

Unlike optocouplers, IsoLoop Isolators are available in MSOP, SOIC, PDIP, 0.15" SOIC-16, and 0.3" SOIC-16 packages. They have up to 6 kV isolation; up to 5 channels per device, up to 150 Mbps, and up to 125°C.

References and further reading

How GMR Works

Magnetic Couplers in Industrial Systems
Sensors Magazine
, 3/02