Power Corner: Allegro’s Anuj Jain on TMR—The New Frontier in Magnetic Sensing

Why It Matters

TMR’s ultra‑high bandwidth and sensitivity enable reliable over‑current protection and precise control in next‑generation wide‑bandgap power systems, a critical need as the industry pushes higher switching frequencies.

Key Takeaways

• TMR offers >1,000× Hall sensor signal and 10 MHz bandwidth
• Allegro’s ACS37100 is first 10 MHz magnetic current sensor
• BEOL integration lets TMR sit atop automotive‑grade BiCMOS wafers
• Crocus acquisition gave Allegro proprietary stack design and low‑defect production
• High‑speed TMR enables safe over‑current protection in GaN/SiC systems

Pulse Analysis

Magnetic sensing has long been dominated by Hall‑effect devices, but the quantum‑mechanical tunnel magnetoresistance (TMR) breakthrough is reshaping the market. By exploiting electron tunneling across ultra‑thin ferromagnetic layers, TMR delivers signal gains exceeding 1,000 × Hall sensors while maintaining bandwidth up to 10 MHz and temperature drift under 3 %. This performance envelope opens doors for applications that demand rapid, low‑noise current measurement—particularly in wide‑bandgap (WBG) power electronics where GaN and SiC transistors switch in the sub‑microsecond regime. Engineers can now detect zero‑crossing events and trigger protection circuits within tens of nanoseconds, improving efficiency and reliability across electric vehicles, data‑center power supplies, and renewable‑energy converters.

Allegro’s strategic acquisition of Crocus Technology supplied the proprietary materials expertise and precision deposition tools needed to mass‑produce TMR stacks with 20‑plus sub‑layers and micron‑scale pillar geometries. By integrating these stacks in a back‑end‑of‑line (BEOL) flow atop existing automotive‑grade BiCMOS processes, Allegro achieves monolithic sensor‑IC solutions that save silicon area and meet stringent automotive reliability standards. The BEOL approach also simplifies supply‑chain logistics, allowing the same wafer platform to host both logic and high‑performance magnetic sensing, a key differentiator in a market where most competitors rely on separate chip assemblies.

The launch of the ACS37100, recognized as an EDN Product of the Year, signals the commercial viability of high‑speed TMR. Its nanowatt power draw makes it suitable for always‑on health‑monitoring wearables, while its 10 MHz bandwidth addresses the critical need for fast over‑current detection in high‑frequency power converters. As EV adoption accelerates and data‑center densities climb, demand for sensors that can keep pace with ever‑higher switching frequencies will surge. Allegro’s end‑to‑end TMR capability positions it to capture a growing share of the magnetic sensor market, driving innovation across power electronics, automotive safety, and emerging robotics domains.