as5045 austriamicrosystems, as5045 Datasheet - Page 12

• Manufacturer Part Number: as5045
• Description: 12-bit Programmable Magnetic Rotary Encoder
• Manufacturer: austriamicrosystems

AS5045 12-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER
10 Choosing the Proper Magnet
Typically the magnet should be 6mm in diameter and
≥2.5mm in height. Magnetic materials such as rare earth
AlNiCo/SmCo5 or NdFeB are recommended.
The magnetic field strength perpendicular to the die
surface has to be in the range of ±45mT…±75mT (peak).
The magnet’s field strength should be verified using a
gauss-meter. The magnetic field B
along a concentric circle with a radius of 1.1mm (R1),
should be in the range of ±45mT…±75mT. (see Figure
16).
Revision 1.2, 03-Oct-06
Figure 16: Typical magnet (6x3mm) and magnetic field distribution
Vertical field
component
Vertical field
component
Bv
0
360
N
(45…75mT)
R1
typ. 6mm diameter
v
R1 concentric circle;
radius 1.1mm
at a given distance,
S
Magnet axis
Magnet axis
360
www.austriamicrosystems.com
10.1
The best linearity can be achieved by placing the center
of the magnet exactly over the defined center of the chip
as shown in the drawing below:
Magnet Placement
The magnet’s center axis should be aligned within a
displacement radius R
center of the IC.
The magnet may be placed below or above the device.
The distance should be chosen such that the magnetic
field on the die surface is within the specified limits (see
Figure 16). The typical distance “z” between the magnet
and the package surface is 0.5mm to 1.5mm, provided
the use of the recommended magnet material and
dimensions (6mm x 3mm). Larger distances are possible,
as long as the required magnetic field strength stays
within the defined limits.
However, a magnetic field outside the specified range
may still produce usable results, but the out-of-range
condition will be indicated by MagINCn (pin 1) and
MagDECn (pin 2), see Table 1.
Die surface
Figure 17: Defined chip center and magnet displacement radius
2.433 mm
2.433 mm
Physical Placement of the Magnet
N
Figure 18: Vertical placement of the magnet
Package surface
1
S
Area of recommended maximum
magnet misalignment
3.9 mm
d
of 0.25mm from the defined
z
1.282mm ± 0.15mm
0.576mm ± 0.1mm
R
d
Defined
center
3.9 mm
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