Magnetic Iso
A magnetic digital isolator transfers digital information between electrically separated circuit domains. Analog Devices' iCoupler technology uses microtransformers for this purpose. Certain isoPower products also integrate isolated power conversion, but a data-isolation channel alone is not a power supply or a complete external-bus interface.
The transmitter encodes input information into changing signals that couple magnetically through an insulated transformer. A receiver reconstructs the logic state. The cited iCoupler architecture includes refresh signaling to preserve a static input state. The isoPower article shows distinct signal and power transformers in one integrated solution, not one universal coil doing every job.
In plain terms
Two coils can pass a changing magnetic signal without joining their wires. The receiver decodes that signal on its own side of the barrier; supplying useful power to that side is a separate design question.
Why designers use it
- Transfer digital signals between suitable isolated circuit domains.
- Avoid using an LED as the signal-coupling element, while still checking the isolator's own lifetime and operating limits.
- Use an appropriately rated combined signal-and-power device when its isolated output meets the secondary-side load.
Best for
- Isolated digital interfaces
- Compatible industrial control
- Signal-and-power isolation designs
Key specifications
- Isolation requirements: Working voltage, test voltage and approvals (These ratings answer different safety questions.)
- Signal behavior: Rate, delay, channel direction and default state (Choose against the complete interface timing requirements.)
- Power and layout: Separate supply or specified isolated output (Follow the exact device's bypassing, spacing and emissions guidance.)
When not to use it
- When the device's working voltage, insulation category, transient behavior or approvals do not meet the system requirement.
- When the data rate, timing, channel direction or available isolated power is unsuitable.
Common mistakes
- Treating a short-duration isolation test voltage as an allowable continuous working voltage.
- Assuming a general logic isolator is itself a complete interface-specific transceiver such as an RS-232 or RS-485 device.
- Assuming all magnetic isolators include isolated power.
- Ignoring board spacing, bypassing and the manufacturer's emissions guidance.
- Promising protection from an arbitrary lightning surge or insulation failure based on one component rating.
Where you will find it
- Analog Devices' article shows ADuM5242 in a secondary-control power-supply example, transferring control signals and providing startup power to the secondary controller.
- AN-0971 examines PCB-related emissions from isoPower implementations and demonstrates layout techniques. Use the guidance for the selected implementation rather than assuming its example board construction fits every isolator.
A short history
The cited Analog Devices article describes microtransformer signal encoding and integrated isolated power conversion. Its die photograph distinguishes signal transformers from power transformers. The separate FAQ distinguishes test voltage, continuous working voltage and transient immunity; AN-0971 addresses board-level emissions. These sources support the operating explanation without establishing universal speed, temperature or safety guarantees.
Good to know
- An unchanged logic input still needs to be represented reliably across the barrier; the cited architecture uses refresh signals.
- The power needed by the receiver and by external loads is a separate requirement from transferring information.