IC-MPEVALMP1D datasheet(8/22 Pages) ICHAUS

8 / 22 page

iC-MP 8-BIT HALL ANGLE ENCODER

WITH RATIOMETRIC OUTPUT

Rev B1, Page 8/22

SENSOR PRINCIPLE

-B

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-

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.

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.

Figure 2: Position of the Hall sensors

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.

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 VSIN = VPSIN -

VNSIN and the cosine VCOS = VPCOS - VNCOS. 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.

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

4 being produced. The signals are internal but can be

made externally available for test purposes (see chap-

ter ’TEST MODES’).

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