as5140 austriamicrosystems, as5140 Datasheet - Page 14

• Manufacturer Part Number: as5140
• Description: 10-bit 360? Programmable Magnetic Rotary Encoder For High Ambient Temperatures Up To 150?c
• Manufacturer: austriamicrosystems

AS5140H 10-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER
12 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 magnet’s field strength perpendicular to the die
surface should be verified using a gauss-meter. The
magnetic field B
circle with a radius of 1.1mm (R1), should be in the range
of ±45mT…±75mT. (see Figure 17).
12.1 Physical Placement of the Magnet
The best linearity can be achieved by placing the center
of the magnet exactly over the defined center of the IC
package as shown in Figure 18:
Revision 1.1, 02-03-2007
Figure 17: Typical magnet and magnetic field distribution
Vertical field
component
Vertical field
component
Bv
v
at a given distance, along a concentric
0
360
N
(45…75mT)
R1
typ. 6mm diameter
R1 concentric circle;
radius 1.1mm
S
Magnet axis
Magnet axis
360
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Magnet Placement:
The magnet’s center axis should be aligned within a
displacement radius R
center of the IC with reference to the edge of pin #1 (see
Figure 18). This radius includes the placement tolerance
of the chip within the SSOP-16 package (+/- 0.235mm).
The displacement radius R
the center of the chip (see section 10:Alignment Mode:).
The vertical distance should be chosen such that the
magnetic field on the die surface is within the specified
limits (see Figure 17). 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 usable results, but the out-of-range condition
will be indicated by MagINCn (pin 1) and MagDECn (pin
2), see Table 3.
Die surface
2.433 mm
2.433 mm
Figure 18: Defined IC center and magnet displacement radius
N
Figure 19: 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
d
is 0.485mm with reference to
z
1.282mm ± 0.15mm
0.576mm ± 0.1mm
R
d
Defined
center
3.9 mm
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