Magnetic sensors have redundancy to meet ASIL D standard

A redundant tunnel-magneto-resistance (TMR) angle sensor from TDK, the TAD4140 has a digital output in a TSSOP16 package for automotive and industrial applications. The new sensor is able to simultaneously measure speed, direction and motor position.

Characterised by high-angular accuracy, high-diagnostic coverage and advanced compensation algorithms, the sensor is suitable, according to TDK, for brushless DC (BLDC) motor commutation applications in electric power assisted steering (EPAS) systems or robot arms.

Compared to TDK’s existing digital angle sensor – the TAD2141 – the TAD4140 features full redundancy with two signal processor units and 2×2 TMR bridges. It is supplied in a single TSSOP16 package and is designed for demanding automotive and industrial applications, says TDK.

Like the earlier model, the TAD4140 angle sensor is capable of contactless sensing up to 360 degrees within an ambient temperature range of -40 to +150 degrees C.

Internal diagnostic features make the digital angle sensor compatible with stringent automotive applications where functional safety is required. It meets the requirements of Automotive Safety Integrity Level D (ASIL D) and is able to support fail-safe applications due to its electrically-isolated signals, high signal availability, and high-diagnostic coverage.

Digital outputs support functionality such as Hall emulation (UVW), encoder up to 12 bits (ENC), incremental encoder (ABZ), pulse width modulation (PWM), and serial peripheral interface (SPI). The built-in redundancy enables the TAD4140 to simultaneously give two different outputs, such as ABZ and ENC, to calculate speed, direction, and motor position. As a result, the sensor can be employed in applications with two electronic control units (ECUs) working in a master/slave configuration, for example in applications like steering motor position detection.

TDK’s TMR technology can be used in combination with a dedicated application specific integrated circuit (ASIC) including an embedded digital signal processor (DSP). The integrated static and dynamic calibration functions can compensate for drifts in gain, offset, or orthogonality. The TAD4140 guarantees an angle accuracy of ±0.35 degrees, achieving the industry’s highest accuracy for angle error of only ±0.05 degrees at room temperature, claims TDK. Mechanical non-idealities including magnet tilting or magnet displacement can also be compensated for, allowing wider assembly tolerances for the mechanical components, adds the company.

The sensors is moulded in a TSSOP16 package with identical pinout on one side of the package. Samples are available now with production planned to start in Q4 2020.

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