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TAS 4240 - small redundant analog TMR angle-sensor for safety-relevant applications

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TAS4240 is a compact, cost-effective, redundant, half-bridge TMR-based sensor for angle and position detection. This article clearly describes and explains the features of TDK's TMR sensors, thus giving valuable information to our customers.

Product Description

A TMR angle sensor from TDK integrates a number of individual TMR elements. Two of them form a TMR half-bridge and two half-bridges form a TMR Wheatstone bridge.

Figure 1: TAS 4240 block diagram

The arrows in figure 1 show the sensitive magnetic-field directions of the TMR bridge structure. If the external magnetic field direction is in parallel to the sensitive magnetic-field direction of a TMR element, its resistance is minimal. If the field direction is anti-parallel, resistance is maximal. The phase difference of the output signals is 90°.

Applying a rotating magnetic field in the plane of the bridges will create sinusoidal signals which can be understood as Sine and Cosine signals. These signals are pairwise combined to form two identical sensors in one package which allow to realize redundant application concepts with high safety compliance and availability. On system level, also fail-operational architectures can be supported which offers new possibilities for efficient and reliable applications.

The TAS/TAA/TAB series comprises highly sensitive analog sensors. They are able to measure angles up to 360° with high accuracy and stability in a wide range of temperature and magnetic-field variations. The TAS4240 enables precise angle measurements in applications where high performance is needed and space is limited. The sensor comes in a compact TSSOP8 package and provides two redundant analog single-ended SIN/COS outputs.

As a 360° angle sensor, TAS4240 is suited to accurately measure the rotor position of BLDC motors used in safety-critical applications, like power steering, brake boosters, or traction motors. The sensor contains four TMR half bridges and provides two independent SIN/COS outputs. Higher safety levels up to ASIL D can then be achieved for the system while offering higher availability of position information even in case of a failure of one of the output signals. Depending on system architectures, fail-operational concepts can also be supported by the sensor.

TDK’s state-of-the-art TMR technology benefits from its long-term expertise in magnetic-sensor technology and optimizes its sensors by successfully integrating sophisticated TMR technology into small packages. The angle accuracy of the sensor remains stable at different temperatures and over the sensor’s lifetime. The deterministic behavior of the TAS4240 in extended magnetic-field ranges opens up new application possibilities, even in demanding environments.

Figure 2: Wheatstone bridge structure of a TMR sensor

Main Applications

  • Commutation of Brushless DC (BLDC) and permanent-magnet synchronous motors (PMSM) in a safety-relevant environment (Electronic Power Steering, Brake booster, etc.)
  • Linear position sensing using an array of TAS4240 sensors
  • Industrial servo motors, automation, encoders, robotics

Main Features and Benefits

  • Contactless 360° angle measurement
  • High angle accuracy of ±1.0° in an ambient temperature range of -40 °C to +150 °C
  • Redundancy: 2 x single-ended output
  • Low power consumption
  • Supports radial sensing concepts
  • Optimized for automotive (AEC-Q100) and industrial applications

Key data

Series TAS4240
Package type TSSOP8
Package dimensions 3 mm x 6.4 mm x 1.1 mm
Angle accuracy ±1.0° or less (over temperature)
±0.3° (TA= 25 °C, typical)
Operating Temp. Range –40 °C up to +150 °C (ambient)
Analog output Single-ended, redundant, 1.5 Vp-p (at Vcc 5.0 V,　Ratiometric)
Bridge resistance 5 kΩ
External Magnetic Field 20 to 80 mT (recommended)

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