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AS5130

Datasheet - Application In form atio n

8.4.4 Magnet Placement

Ideally, the center of the magnet, the diagonal center of the IC and the rotation axis of the magnet should be in one vertical line. The lateral

displacement of the magnet should be within ±0.25mm from the IC package center or +/-0.5mm from the IC center, including the placement of

the chip within the IC package. The vertical distance should be chosen such that the magnetic field on the die surface is within the specified

limits. The typical distance “z” between the magnet and the package surface is 0.5mm to 1.8mm with the recommended magnet (6mm x 2.5mm).

Larger gaps are possible, as long as the required magnetic field strength stays within the defined limits. A magnetic field outside the specified

range may still produce acceptable results, but with reduced accuracy. The out-of-range condition will be indicated, when the AGC is at the limits

(AGC= 0: field too strong; AGC=63=(3FH): field too weak or missing magnet).

Figure 29. Bz Field Distribution Along the X-axis of a 6mmØ Diametric Magnetized Magnet

Figure 29 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 Bz follows a fairly linear pattern up to about 1.5mm radius. Consequently, even if the magnet is not 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 Bz amplitude becomes nonlinear, which results in larger

errors that mainly affect the accuracy of the system (see Figure 31).

Bz; 6mm magnet @y=0; z=1mm

-0.0015

-0.001

-0.0005

0.0005

0.001

0.0015

-3.5

-2.5

-1.5

-0.5

0.5

1.5

2.5

3.5

X-displacement [mm]

AS5130 Datasheet(PDF) 35 Page - ams AG