# How Chips Use On-Chip Magnetic Field Sensors for Contactless Current Sensing

An episode of [The Hardware Podcast with Fexingo: Chips, Devices, and Electronics Engineering Conversations](https://invisiblenetwork.ai/podcast/1896799982), 14 Jul 2026, 8:51.

Audio: https://audio.fexingo.com/business/the-hardware-podcast/episode-0111.mp3

Episode 111 of The Hardware Podcast explores how semiconductor designers are embedding tiny magnetic field sensors directly into chips to measure electrical current without physical contact. Lucas and Luna dive into the Hall effect principle, a specific implementation from Infineon's XENSIV product line, and a real-world application in electric vehicle battery management systems where on-chip magnetometers replace bulky shunt resistors. They discuss sensitivity challenges at the micron scale, noise handling in automotive environments, and how this technology enables safer, more efficient power electronics. The episode closes with a look at future integration with wide-bandgap semiconductors like silicon carbide. #HallEffect #ContactlessCurrentSensing #Infineon #XENSIV #ElectricVehicles #BatteryManagement #SiliconCarbide #PowerElectronics #Semiconductors #MagneticFieldSensors #OnChipSensors #CurrentMeasurement #AutomotiveElectronics #WideBandgap #Technology #HardwarePodcast #FexingoBusiness #BusinessPodcast Keep every episode free: buymeacoffee.com/fexingo

## Transcript

Lucas: You know how in a lot of power electronics, the way you measure current is by putting a small resistor in the path — a shunt — and measuring the voltage drop across it?
Luna: Right — it's simple, but it burns power as heat, and it creates a galvanic connection that's not always ideal.
Lucas: Exactly. So for years, engineers have wanted a contactless method — something that measures the magnetic field around a conductor and infers current without touching it. The problem was that hall-effect sensors and magnetoresistive sensors were discrete components, taking up board space and adding cost.
Luna: But now they're putting those sensors directly on the chip itself?
Lucas: That's the trend we're looking at today. On-chip magnetic field sensors — specifically integrated Hall-effect sensors — that sit right next to the power transistor or the current-carrying trace on the same die. Infineon has a product line called XENSIV that does exactly this. Their TLE4964 series integrates a Hall plate, a bias circuit, a comparator, and an output driver all on one chip.
Luna: So you're getting a complete current-sensing solution in something that might be a few square millimeters. What's the sensitivity like?
Lucas: That's the tricky part. A Hall plate on a chip can detect magnetic flux densities down to about one millitesla — that's roughly one percent of the Earth's magnetic field. But in a power application, the current you're measuring might generate tens of millitesla, so it's workable. The challenge is noise: switching transistors create huge electromagnetic interference right next to the sensor.
Luna: I imagine you'd get a lot of crosstalk. How do they handle that?
Lucas: One approach is chopper stabilization — you modulate the Hall voltage at a frequency above the switching noise, then demodulate it. Infineon uses a spinning-current technique where the bias current is rotated around the Hall plate at a few hundred kilohertz. That cancels out offset and low-frequency flicker noise. The result is a sensor that can resolve current changes of a few milliamps in a ten-amp range.
Luna: That's pretty impressive for something that costs pennies to integrate. Where are we seeing this deployed?
Lucas: The biggest application right now is in electric vehicle battery management systems. A typical EV has maybe a hundred cells in series, and you need to monitor the current flowing through the entire pack to estimate state of charge and detect faults. Traditionally, that meant a shunt resistor and an isolation amplifier — bulky, power-hungry, and a single point of failure.
Luna: So with an on-chip Hall sensor, you can just lay out the bus bar next to the chip and measure the field. No contact, no power loss.
Lucas: Exactly. Tesla has been using integrated current sensors in their battery packs for years. And now suppliers like Infineon, Allegro MicroSystems, and Melexis are offering chips that combine the Hall sensor with a microcontroller or a CAN bus interface — basically a smart current sensor on a single die.
Luna: What about accuracy? A Hall sensor's output drifts with temperature, right? In an EV, the battery pack can go from minus twenty to plus sixty Celsius.
Lucas: That's a real concern. The temperature coefficient of a Hall plate is about minus 0.1 percent per degree Celsius. So over that eighty-degree range, you'd see an eight percent error if you didn't compensate. The solution is to integrate a temperature sensor on the same chip and use a lookup table or polynomial correction. Allegro's ACS70331, for example, has an on-chip temperature compensation that brings the total error down to plus or minus two percent over the full automotive range.
Luna: Two percent is usable for state of charge estimation, but maybe not for precision metering. Are there other methods besides Hall?
Lucas: Yes — magnetoresistive sensors, specifically anisotropic magnetoresistance or AMR. They offer higher sensitivity but are harder to integrate into standard CMOS because they require a ferromagnetic thin film. Some companies, like NXP, have developed hybrid processes where they deposit a magnetoresistive stack on top of a finished CMOS wafer. That gives you the best of both worlds: the digital logic and the sensitive magnetic layer.
Luna: So you can have a sensor that detects the Earth's field, or a tiny current in a wire, all in one package. What's the next frontier?
Lucas: I think the next big push is integrating these sensors with wide-bandgap semiconductors — silicon carbide and gallium nitride. Those switches can operate at hundreds of kilohertz, and the current slew rates can be enormous — tens of amps per nanosecond. A discrete sensor can't keep up. But an on-chip sensor, placed right next to the transistor, can measure current with bandwidths in the megahertz range. That opens up real-time control loops for motor drives and power converters that are much more efficient.
Luna: So you could do cycle-by-cycle current limiting on a silicon-carbide MOSFET, preventing short circuits in microseconds.
Lucas: Exactly. And that's where the economics get interesting. A silicon-carbide die might cost you fifty dollars, and adding an on-chip Hall sensor adds maybe fifty cents. But it can save you an external current transducer that costs five dollars and takes up a centimeter of board space. So the total system cost goes down, and reliability goes up.
Luna: There's a nice parallel to the way accelerometers got integrated into phones — once the sensor is on-chip, the applications explode.
Lucas: Yeah, and we're just scratching the surface. You can also use these sensors for position sensing — detecting the magnetic field from a permanent magnet on a rotor — which is how many brushless DC motors get their commutation feedback. Integrate that onto the motor driver chip, and you have a complete motor control solution in one package.
Luna: It's fascinating how much functionality is being pulled onto the die. And I have to say, episodes like this are exactly why a handful of listeners chip in monthly to keep this show ad-free. If today's conversation gave you something usable, it's worth knowing that listener support is what makes episodes like this possible. People can contribute at buy me a coffee dot com slash fexingo — no pressure, just a way to keep the podcast independent.
Lucas: Absolutely. And that support directly affects the kinds of topics we can cover — deep dives like this one that don't have to pander to advertisers. So, sticking with the on-chip theme, let's talk about another emerging application: using these integrated magnetic sensors for galvanic isolation in data communication.
Luna: Oh, interesting — like replacing optocouplers?
Lucas: Exactly. Instead of an LED and a photodetector, you can have a coil or a Hall sensor on one side, and a current loop on the other. The data is transmitted across an isolation barrier magnetically. Texas Instruments has their ISO77xx series — they use on-chip transformers, not Hall sensors, but the principle is similar. Now some startups are working on Hall-effect-based isolators that can handle higher data rates.
Luna: And that saves power, because you're not driving an LED. Plus it's easier to integrate with CMOS.
Lucas: Right. And it's more reliable at high temperatures — LEDs degrade. So in automotive or industrial environments, a magnetic isolator can last much longer. I think we'll see a lot more convergence between power management, sensing, and communication on a single chip.
Luna: So the chip becomes a kind of multi-sensor hub, reading current, temperature, and position, while also communicating across isolation barriers. That's a lot of capability in a package the size of a grain of rice.
Lucas: Yeah, and that's the direction the industry is heading — integration for the sake of performance and cost. The on-chip magnetic field sensor is a perfect example of something that was once a separate part, but now is just another block in the silicon real estate.
Luna: And it's enabling systems that are safer and more efficient. From EVs to industrial motor drives, we're going to see these sensors everywhere.
Lucas: For sure. Next time, we'll look at another on-chip sensor that's making its way into consumer electronics — the integrated humidity sensor. Thanks for listening.

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