Dual Hall sensor detects rotation direction and speed

December 18, 2013 // By Christoph Hammerschmidt
Infineon has developed a vertical dual-Hall sensor for detecting rotation direction and speed. The TLE4966V is the first dual-Hall device with its integrated Hall plates oriented vertically instead of horizontally on the chip surface, making it sensitive to magnetic fields with in-plane direction. This 90-degree orientation change provides flexibility to fit designs into space-constrained areas. 

Its design flexibility and low current consumption make the TLE4966V suited for energy-sensitive electronic automotive systems such as trunk lifts, power window lifts, sun roofs and seat adjustment. In non-automotive applications, the sensor can also be utilized for escalators, motorized window blinds and shades. 

The sensor is an extension of Infineon's TLE4966 family frequently used in window lifter and other index counting applications. This product family is designed to detect the rotation direction and rotation speed of a magnetic pole wheel. The vertically integrated Hall plates in the new TLE4966V enable sensing of in-plane, instead of perpendicular, magnetic fields. Changing sensing orientation by 90 degrees allows system engineers to design new and previously unattainable mechanical concepts, in particular for for space-restricted applications such as power window lifts and electronic trunk lifts. 

Detecting the direction and speed of rotation of a magnetic pole wheel requires two separate Hall plates. Due to the distance between the two plates, they detect slightly different signals at any time. This is termed the phase difference. During a rotation direction change, the phase difference changes polarity. The TLE4966V detects this change and delivers a corresponding signal. The rotation speed of a magnetic pole wheel can directly be calculated with the second sensor output signal. This signal is triggered by each polarity change of the magnetic field.

The two integrated vertical Hall plates on a single silicon die within the TLE4966V feature the same behaviour for temperature and lifetime stress, with no sensitivity deviation over lifetime. Furthermore, the TLE4966V has two signal outputs: one signal for the magnet rotation direction, the other signal for the pole wheel rotation speed. That means that a single device delivers all relevant information where previously two sensors have been required. Eliminating a separately packaged sensor can simplify the PCB design, reduce sensor cost by an average of 30 percent and lower test and manufacturing time by up to 50