AS5030 8-bit Programmable Magnetic Rotary Encoder

Rev. 1.8

www.austriamicrosystems.com

Page 27 of 33

Figure 32 shows a cross sectional view of the vertical magnetic field component Bz between the north and south pole of a 6mm

diameter magnet, measured at a vertical distance of 1mm. The poles of the magnet (maximum level) are about 2.8mm from the

magnet center, which is almost at the outer magnet edges. The magnetic field reaches a peak amplitude of

~±

106mT at the poles.

The Hall elements are located at a radius of 1mm (indicated as squares at the bottom of the graph). Due to the side view, the

two Hall elements at the Y-axis are overlapping at X = 0mm, therefore only 3 Hall elements are shown.

At 1mm radius, the peak amplitude is ~± 46mT, respectively a differential amplitude of 92mT.

perfectly centered, the differential amplitude will be the same as for a centered magnet.

For example, if the magnet is misaligned in X-axis by -0.5mm, the two X-Hall sensors will measure 70mT (@x = -1.5mm) and

-22mt (@x = -0.5mm). Again, the differential amplitude is 92mT.

accuracy of the system (see also Figure 34)

4

3

2

1

0

-1

-2

-3

-4

4

3

2

2

1

0

-1

-2

-3

-125

-100

-75

-50

-25

0

25

50

75

100

125

Bz [mT]

Y-displacement [mm]

X-displacement [mm]

BZ; 6mm magnet @ Z=1mm

area of X-Y-misalignment from

center: +/- 0.5mm

circle of Hall elements on

chip: 1mm radius

N

S

Figure 33: Vertical magnetic field distribution of a cylindrical 6mm Ø diametric magnetized magnet at 1mm gap

Figure 33 shows the same vertical field component as Figure 32, but in a 3-dimensional view over an area of ± 4mm from the

rotational axis.

10.2 Lateral displacement of the magnet

As shown in the magnet specifications (4.4), the recommended horizontal position of the magnet axis with respect to the IC

package center is within a circle of 0.25mm radius. This includes the placement tolerance of the IC within the package.

Figure 34 shows a typical error curve at a medium vertical distance of the magnet around 1.2mm (AGC = 24).

The X- and Y- axis of the graph indicate the lateral displacement of the magnet center with respect to the IC center.

At X = Y = 0, the magnet is perfectly centered over the IC. The total displacement plotted on the graph is for ± 1mm in both

directions.

The Z-axis displays the worst case INL error over a full turn at each given X-and Y- displacement. The error includes the

quantization error of ± 0.7° (see 0). For example, the accuracy for a centered magnet is between 1.0 ~ 1.5° (spec = 2° over full

temperature range). Within a radius of 0.5mm, the accuracy is better than 2.0° (spec = 3° over temperature).