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TLE5012B
Functional Description
User’s Manual
14
Rev. 1.2, 2018-02
2.3
Sensing Principle
The Giant Magneto Resistance (GMR) sensor is implemented using vertical integration. This means that the
GMR-sensitive areas are integrated above the logic part of the TLE5012B device. These GMR elements change
their resistance depending on the direction of the magnetic field.
Four individual GMR elements are connected to one Wheatstone sensor bridge for each of the two components
of the applied magnetic field:
•
X component, V
x
(cosine) and the
•
Y component, V
y
(sine)
With this full-bridge structure the maximum GMR signal is available and temperature effects cancel out each other.
Figure 2-4 Sensitive bridges of the GMR sensor (not to scale)
Attention: Due to the rotational placement inaccuracy of the sensor IC in the package, the sensors 0°
position may deviate by up to 3° from the package edge direction indicated in
.
, the arrows in the resistors represent the magnetic direction which is fixed in the Reference Layer.
On top of the Reference Layer, and separated by a non magnetic layer, there is a Free Layer. When applying an
external magnetic field the Free Layer moves in the same direction as the external magnetic field, while the
Reference Layer remains fix. The resistance of the GMR elements depends on the magnetic direction difference
between the Reference Layer and the Free Layer.
When the external magnetic field is parallel to the direction of the Reference Layer, the resistance is minimal
(Reference Layer and Free Layer are parallel). When the external magnetic field and the Reference Layer are anti-
parallel (Reference Layer and Free Layer are anti-parallel), resistance is maximal.
The output signal of each bridge is only unambiguous over 180° between two maxima. Therefore two bridges are
oriented orthogonally to each other to measure 360°.
With the trigonometric function ARCTAN2, the true 360° angle value is calculated out of the raw X and Y signals
from the sensor bridges.
V
DD
GND
ADC
X
+
GMR Resistors
ADC
X
-
ADC
Y
+
ADC
Y
-
V
X
V
Y
0°
N
S
90°