iC-MP
8-BIT HALL ANGLE ENCODER
WITH RATIOMETRIC OUTPUT
Rev B1, Page 8/22
SENSOR PRINCIPLE
coder system or a contactless potentiometer. A dia-
metrically magnetized, cylindrical permanent magnet
made of neodymium iron boron (NdFeB) or samarium
cobalt (SmCo) generates optimum sensor signals. The
diameter of the magnet should be in the range of 3 mm
to 6 mm.
The iC-MP 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 oppo-
site direction. Figure 1 shows an example of field vec-
tors.
The arrangement of the Hall sensors is selected so
that the mounting of the magnets relative to iC-MP 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.
S
N
z
y
x
B
+B
z
-B
z
C151107-1
Figure 1: Sensor principle
In conjunction with a rotating permanent magnet, the
iC-MP module can be used to create a complete en-
HALL SENSOR POSITION AND INTERNAL ANALOG SIGNALS
The Hall sensors are placed in the center of the DFN10
package at 90° to one another and arranged in a circle
with a diameter of 2 mm as shown in Figure 2.
In order to calculate the angle position of a diametri-
cally polarized magnet placed above the device a dif-
ference in signal is formed between opposite pairs of
Hall sensors, resulting in the sine being V
SIN
= V
PSIN
-
V
NSIN
and the cosine 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 3. Sensors
PSIN and NSIN are placed along the pole boundary so
that neither generate a Hall signal.
Figure 2: Position of the Hall sensors
When the magnet is rotated counterclockwise the
poles then also cover the PSIN and NSIN sensors, re-
sulting in the sine and cosine signals shown in Figure
made externally available for test purposes (see chap-
ter ’TEST MODES’).
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.
ICHAUS [ IC-HAUS GMBH ]
