# On-Chip Microtransformers Shrink Isolated Power

An episode of [The Hardware Podcast with Fexingo: Chips, Devices, and Electronics Engineering Conversations](https://invisiblenetwork.ai/podcast/1896799982), 25 Jul 2026, 6:31.

Audio: https://audio.fexingo.com/business/the-hardware-podcast/episode-0131.mp3

Lucas and Luna explore how microtransformers integrated directly onto silicon are revolutionizing isolated power conversion. They discuss recent research from the University of Twente demonstrating a 5-kilovolt isolation transformer in less than a square millimeter, the challenges of magnetic core integration and winding resistance, and applications in electric vehicles, medical implants, and data centers. The hosts also explain why this technology is key to shrinking power supplies for GaN-based systems and how it could replace discrete transformers in millions of devices. #Hardware #Engineering #Chips #Microtransformers #PowerConversion #IsolatedPower #GaN #ElectricVehicles #MedicalDevices #DataCenters #CMOS #MagneticComponents #EnergyEfficiency #ThermalManagement #FexingoBusiness #BusinessPodcast #Technology #Electronics Keep every episode free: buymeacoffee.com/fexingo

## Transcript

Lucas: You know, when you think about the components that haven't shrunk much in the last few decades, power transformers are near the top of the list.
Luna: They're still these bulky toroids or E-cores, right? Even in modern chargers.
Lucas: Exactly. But there's a growing push to integrate transformers directly onto the chip itself. Last month, a team at the University of Twente published results showing a microtransformer that handles 5 kilovolts of isolation in a die area less than a square millimeter.
Lucas: A lot of the research we cover comes from open-access papers and independent labs — and keeping this show ad-free and independent is something we're committed to.
Luna: Yeah, if you've gotten something out of our episodes, a couple of dollars a month makes a real difference. You can find us at buy me a coffee dot com slash fexingo.
Lucas: It genuinely helps us keep digging into the details. So, back to those microtransformers — what makes this possible is a combination of advanced lithography and new magnetic materials.
Luna: Right. Typically, integrating a transformer on-chip means you need a magnetic core material that can be deposited and patterned with standard CMOS processes.
Lucas: The Twente team used a thin film of cobalt zirconium tantalum — a soft magnetic alloy — sputtered directly onto the silicon substrate. They then patterned a spiral copper winding above and below the core, creating a fully planar transformer.
Luna: And the isolation? How do they get 5 kilovolts across a chip that's essentially flat?
Lucas: It comes down to the thickness and quality of the silicon dioxide and polyimide layers between the windings. By carefully controlling the dielectric breakdown strength, they can stack multiple layers of insulation that together withstand high voltages.
Lucas: One of the key metrics here is the coupling coefficient — how well the primary and secondary windings transfer energy. They achieved a coefficient of 0.85, which is pretty impressive for an on-chip transformer.
Luna: That's not far from discrete transformers, which can hit 0.95 or higher. So the gap is closing.
Lucas: Absolutely. And where this really matters is in applications that already benefit from gallium nitride power devices. GaN transistors can switch at tens of megahertz, but they need a gate driver that's isolated from the high-voltage side. A discrete transformer adds size and inductance that limits switching speed.
Luna: So an on-chip microtransformer could sit right next to the GaN transistor, driving it with minimal parasitic inductance.
Lucas: Exactly. Researchers at Texas Instruments have already demonstrated integrated isolation in their UCC120xx series, but those use capacitive coupling, not magnetic. Capacitive isolators have lower power density and are more sensitive to common-mode transients. Magnetic gives you better efficiency and higher power transfer.
Luna: What about the power levels? Five kilovolts isolation is great, but how much current can these microtransformers handle?
Lucas: The Twente device is designed for a few hundred milliwatts — enough for gate drivers and isolated sensors. But there's work from MIT and Stanford pushing toward watt-level power transfer using thicker copper and larger cores.
Lucas: For example, a Stanford group last year showed a microtransformer with an integrated magnetic core that could deliver 2.5 watts at 85% efficiency — enough to power a small sensor node or a medical implant.
Luna: Medical implants are a great use case because you need galvanic isolation to prevent any leakage current from reaching the patient.
Lucas: Right. And the size reduction is dramatic. A conventional medical-grade isolation transformer might be a cubic centimeter or more. An on-chip version fits in a chip-scale package, maybe 2 millimeters square.
Luna: That could enable completely new form factors for pacemakers, neurostimulators, or even ingestible sensors.
Lucas: Another big application is in electric vehicle battery management systems. They need isolated communication between the high-voltage battery pack and the low-voltage controller. Currently that uses optocouplers or discrete transformers. An on-chip magnetic isolator could be smaller and more reliable.
Lucas: The key challenge is the manufacturing yield. Depositing a magnetic core that's uniformly thick and has the right magnetic properties across an entire wafer is tough. Any variation shifts the inductance and coupling.
Luna: Are there any companies commercializing this yet?
Lucas: A startup called Mosaic Power spun out of Twente is aiming for production in 2027. They're targeting isolated gate drivers for SiC and GaN power modules. There's also a company called Power Integrations that's been developing integrated transformers for flyback converters, though those are still hybrid solutions.
Luna: So it sounds like we're at the inflection point where on-chip magnetics go from research curiosity to real products.
Lucas: I think so. In the next three to five years, I'd expect to see these microtransformers embedded in standard power management ICs, especially for applications that demand high switching frequencies and small footprints.
Lucas: One more thing: the same technology can be used to create integrated inductors for dc dc converters. That's a related but distinct challenge because inductors don't need isolation, but they do need high saturation current.
Luna: Right, and the same magnetic films can be used for both inductors and transformers. So it's a platform technology.
Lucas: Exactly. And that platform could help shrink everything from phone chargers to server power supplies. A 300-watt server power supply today uses a handful of bulky magnetic components. If you can integrate most of those onto silicon, you cut the volume in half.
Luna: And efficiency goes up because you eliminate interconnect losses between discrete parts.
Lucas: Right. The future is integrated, and microtransformers are a big piece of that puzzle.
Luna: Great topic. I'm excited to see where this goes.

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