Introduction
As electromobility continues to close the cost gap with combustion powertrains, e-motor programs face growing pressure to improve performance without adding packaging complexity, wiring overhead, or EMC risk. Rotor position sensing sits right at this intersection — it directly shapes torque quality, efficiency, and thermal behavior, while influencing how the motor housing is designed and how the harness is routed.
TE Connectivity’s TMR rotor position sensor addresses this challenge with a compact, digital approach that combines rare-earth-free magnetics, synchronized ECU sampling, and a four-wire CAN physical layer interface. This whitepaper outlines how the technology works, where it fits relative to legacy sensing approaches, and what it means for system-level cost and integration across multi-platform e-motor programs.
You Will Learn
- How TMR sensing technology differs fundamentally from resolver and inductive eddy-current approaches
- Why the ferrite Halbach ring magnet eliminates rare-earth dependency while boosting signal-to-noise performance
- How the spring-mounted magnet carrier provides simultaneous mechanical retention and local EMC shielding
- What TE’s patented high-speed triggering achieves in terms of latency and acquisition jitter
- How a single hardware variant covers multiple motor pole counts through software-only pole-pair scaling
- What end-to-end timing performance looks like across the full ECU trigger-to-PWM-update cycle
- How the CAN physical layer interface reduces harness conductor count and connector diversity
- What continuous diagnostics and CRC framing mean for functional safety and ASIL target support
- How the compact form factor reduces motor housing machining complexity and assembly steps
- Where the system-level cost savings are realized across materials, logistics, and validation effort
Strategic Insight: A Smaller Sensor Can Mean a Fundamentally Simpler Motor Program
TMR Directly Measures the Field — No Excitation Hardware Required
Unlike resolvers, which rely on excited sine and cosine windings with analog demodulation in the ECU, or inductive sensors that require HF coil evaluation, a TMR sensor measures the magnetic field directly through tunnel junction resistance changes. This eliminates excitation hardware entirely and allows signal conditioning to be integrated with a fully digital output. The result is a PCB-less module in a camshaft-class form factor that delivers absolute rotor angle from standstill to maximum speed without adding analog front-end complexity to the ECU.
The Halbach Ring Does Two Jobs at Once
The ferrite Halbach ring at the core of the design concentrates magnetic flux toward the sensing element while cancelling it on the opposite side. This geometry inherently raises signal-to-noise ratio and reduces sensitivity to air-gap and concentricity variations — two of the most common sources of accuracy degradation in real-world motor environments. By eliminating rare-earth materials, it also removes a meaningful supply chain risk that is increasingly relevant for high-volume EV programs.
Four Wires, Deterministic Timing, and Protocol-Level Integrity
The CAN physical layer interface replaces analog sine and cosine leads with a single differential pair carrying timestamped, CRC-protected angle frames with sequence counters and diagnostics. TE’s patented high-speed triggering synchronizes angle acquisition directly to ECU PWM update windows, keeping angle age below 12 microseconds. This level of timing determinism tightens d/q-axis alignment, reduces torque ripple, and improves transient response — benefits that arrive without any additional packaging volume or harness complexity.
One Hardware Part Number Across Multiple Motor Platforms
Because electrical angle is derived through software-only pole-pair scaling, a single physical sensor variant supports motors with different pole counts. Combined with simplified motor housing geometry — no additional oil-tight pass-throughs or connectors at the motor end — this collapses validation effort, reduces logistics complexity, and shortens the integration timeline across vehicle lines.
Governance and Challenges
Functional safety requirements for e-motor sensing demand continuous diagnostic coverage, deterministic fault response, and graceful degradation under disturbance. Organizations evaluating new sensing approaches must assess ASIL compatibility, frame integrity mechanisms, and redundancy path handover behavior within their existing ECU architectures. EMC performance in high-power inverter environments also requires careful attention to shielding design and cable routing practices.
Implementation and Strategy
Adopting the TMR platform begins with evaluating the motor housing design for sensor cavity sizing and fixture simplification opportunities. Software-side integration involves configuring pole-pair scaling and calibration profiles for the target motor topology. The four-wire CAN interface aligns with standard automotive harness practices, minimizing new connector qualification requirements. TE’s support team at te.com/support is available to assist with application-specific configuration and integration guidance.
Who Should Read This
This whitepaper is essential reading for e-motor system architects and powertrain engineers evaluating next-generation sensing technologies, ECU and control software teams working on torque control and observer alignment, EMC and harness engineers managing integration complexity in high-power drive environments, and procurement and platform leads assessing multi-program sensor standardization strategies across EV programs.
Download A Compact, Digital Tunnel Magnetoresistance (TMR) Rotor Position Sensor for Next-Generation E-Motors from TE Connectivity to explore the full technical architecture, timing diagrams, and system-level integration considerations for your e-motor program.
