Triaxis®: Unique sensing solution

Triaxis® is an innovative magnetic sensor technology capable of very precise three axis magnetic field measurements from a single sensor. Endless linear, angular and 3D applications can be developed.

Traditional Hall sensors are only sensitive to the magnetic flux density perpendicular to the surface of the Hall element and consequently of the IC and package. These single-axis devices, despite enabling some applications, often require complex magnetic structures and face accuracy challenges especially over a wide temperature range (due to the thermal drift of the measured magnet).

Triaxis® sensors, on the other hand, are based on a patented innovative magnetic sensor technology that enables measurement of the three magnetic flux components (BX, BY and BZ) in a single integrated circuit. This is done by utilizing a unique Integrated Magnetic Concentrator (IMC®). Using the three magnetic components, it is possible to create 2D or 3D sensors that determine rotary (angle), linear (stroke), or even joystick type motion as well as 3D-magnetometers that can output the individual magnetic (BX, BY, and BZ) components.

Strengths of Triaxis® sensors

Triaxis® sensors are small, capable of high-temperature operation and can support a wide variety of sensing applications by adjusting the on-chip magnetic angle computation. Since the angular computation is a relative measurement between two or three magnetic flux components, the measurement is robust to temperature variations but also magnetic and mechanical (for example airgap, eccentricity) tolerances. With an additional calibration process performed after module assembly, excellent linearity and accuracy can be obtained thanks to the on-chip parameters (such as 4 up to 32-pts calibration). The high sensitivity and flexibility allows a wide range of magnet shapes (disc, rod, square...) and chemistry (ferrite, NeFeB, SmCo, AlNiCo…) to be used while still reaching a high accuracy.

The sensors are intrinsically insensitive to dirt, dust, oil, gas and other contaminants because the magnetic field is being sensed in a non-contacting manner. The IC itself can be overmolded in plastic or potted to protect the IC from these contaminants and ensure long life even when exposed to harsh media.

Third generation Triaxis® position sensors

Building upon the long legacy of the Triaxis® sensors, the third generation, already a success with our lead customers, brings substantial improvements over the previous generations. Its new stray field immune mode drastically reduces or eliminates the effect of stray fields from other magnets or current carrying conductors found in electrified vehicles and supports both on-axis rotary or linear motion with a four-pole or two-pole magnet, respectively.

This stray field immune mode reduces design constraints especially in electrified vehicles and meets OEM requirements for stray fields up to 4kA/m. Additionally, the 160°C operating temperature capability allows for use in actuators exposed to hot environments like a turbocharger wastegate while the enhanced linearization capability minimizes accuracy errors caused by tolerances in the mechanical assembly.

In addition to being the first to be ASIL-C (SEooC) ready, this generation also offers other improvements including improved EMC capability and thermal drift performance.

Triaxis® is a unique and innovative magnetic sensor technology capable of very precise three axis magnetic field measurement from a single sensor.

Triaxis® sensor packages

A variety of IC packages are available from the industry standard SOIC-8, TSSOP-16, and QFN-16 to the Melexis Dual-Mold Package (DMP-4).

The SOIC-8, QFN-16, and DMP-4 all contain a single sensor die. The TSSOP-16 contains two sensor dies that are fully independent with unique supply, ground, and output pins enabling redundant operation for systems requiring a higher level of safety or availability. The DMP-4 is intended to be integrated without a PCB via a direct connection to the connector lead frame via welding or soldering which brings packaging, system cost, and reliability advantages.

Finally, Triaxis® sensors are ASIL-ready and contain a suite of onboard diagnostics to ensure safe and correct operation. Melexis can provide additional supporting documentation (Safety Manual) to conduct the necessary safety analysis to ensure ASIL/ISO26262 requirements are met.

Triaxis® sensors usage

Triaxis® sensors are used for automotive position sensing in different applications like steering angle, pedal position, electronic throttle body, EGR valve, shifter, turbo actuator, motor position, chassis height, and more. There are also other fields where Triaxis® sensors could be used, beyond automotive. To name a few applications: Agricultural vehicles and equipment, joysticks, man-machine interfaces, heavy-duty vehicles, forklifts, robots, wheelchairs, industrial cranes, and more.

Want to learn more about the stray field immunity feature of the third generation?
Read these technical papers:

• A Gradiometric Magnetic Sensor System for Stray-Field-Immune Rotary Position Sensing in Harsh Environment by Samuel Huber, Jan-Willem Burssens, Nicolas Dupré, Olivier Dubrulle, Yves Bidaux, Gael Close, Christian Schott
• Experimental Demonstration of Stray-Field Immunity beyond 5 mT for an Automotive-Grade Rotary Position Sensor by Nicolas Dupré, Olivier Dubrulle, Samuel Huber, Jan-Willem Burssens, Christian Schott, Gael Close