as5030 austriamicrosystems, as5030 Datasheet - Page 27

• Manufacturer Part Number: as5030
• Description: 8-bit High-speed Absolute Magnetic Rotary Encoder
• Manufacturer: austriamicrosystems

AS5030 8-bit Programmable Magnetic Rotary Encoder
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.
The vertical magnetic field B
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.
At larger displacements however, the B
accuracy of the system (see also Figure 34)
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).
Rev. 1.8
Bz [mT]
Figure 33: Vertical magnetic field distribution of a cylindrical 6mm Ø diametric magnetized magnet at 1mm gap
125
100
X-displacement [mm]
75
-100
50
-25
-125
25
-50
-75
0
z
follows a fairly linear pattern up to about 1.5mm radius. Consequently, even if the magnet is not
4
3
2
z
amplitude becomes nonlinear, which results in larger errors that mainly affect the
2
BZ; 6mm magnet @ Z=1mm
1
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N
0
-1
-2
-3
-4
S
-3
-2
-1
Y-displacement [mm]
0
1
area of X-Y-misalignment from
center: +/- 0.5mm
2
circle of Hall elements on
chip: 1mm radius
3
4
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