IC-MH_17 Datasheet, PDF (10/26 Pages) IC-Haus GmbH – 12-BIT ANGULAR HALL ENCODER

iC-MH
12-BIT ANGULAR HALL ENCODER
SENSOR PRINCIPLE
Rev C2, Page 10/26
S
N
z
y
B
+B_z
x
-B_z
Figure 2: Sensor Principle
In conjunction with a rotating permanent magnet, the
iC-MH module can be used to create a complete en-
coder system. A diametrically magnetized, cylindrical
permanent magnet made of neodymium iron boron (Nd-
FeB) or samarium cobalt (SmCo) generates optimum
sensor signals. The diameter of the magnet should be
within the range of 3 to 6 mm.
The iC-MH has four Hall sensors adapted for angle
determination and to convert the magnetic field into
a measurable Hall voltage. Only the z component of
the magnetic field is evaluated, whereby the field lines
pass through two opposing Hall sensors in the opposite
direction. Figure 2 shows an example of field vectors.
The arrangement of the Hall sensors is selected so
that the mounting of the magnets relative to iC-MH is
extremely tolerant. Two Hall sensors combined provide
a differential Hall signal. When the magnet is rotated
around the longitudinal axis, sine and cosine output
voltages are produced which can be used to determine
angles.
HALL SENSOR SIGNALS
The Hall sensors are placed in the center of the QFN28
package at 90° to one another and arranged in a circle
with a diameter of 2 mm as shown in figure 3.
Pin 1 Mark
28 27 26 25 24 23 22
(top view)
1
2 _PSIN
3
4
5
6 _NCOS
7
21
PCOS ²⁰
19
18
17
NSIN ¹⁶
15
8 9 10 11 12 13 14
C040907-2
Figure 3: Position of the Hall sensors
In order to calculate the angle position of a diametrically
polarized magnet placed above the device a difference
in signal is formed between opposite pairs of Hall sen-
sors, resulting in the sine being V_SIN = V_PSIN - V_NSIN and
the cosine being V_COS = V_PCOS - V_NCOS. The zero angle
position of the magnet is marked by the resulting cosine
voltage value being at a maximum and the sine voltage
value at zero.
This is the case when the south pole of the magnet is
exactly above the PCOS sensor and the north pole is
above sensor NCOS, as shown in figure 4. Sensors
PSIN and NSIN are placed along the pole boundary so
that neither generate a Hall signal.
When a magnetic south pole comes close to the sur-
face of the package the resulting magnetic field has a
positive component in the +z direction (i.e. from the top
of the package) and the individual Hall sensors each
generate their own positive signal voltage.
When the magnet is rotated counterclockwise the poles
then also cover the PSIN and NSIN sensors, resulting
in the sine and cosine signals being produced as shown
in figure 5. The signals are internal but can be made ex-
ternally available for test purposes (see the description
of iC-MH’s calibration procedure).