as5046 austriamicrosystems, as5046 Datasheet - Page 28

• Manufacturer Part Number: as5046
• Description: Programmable 12-bit 360? Magnetic Angle Encoder With Absolute 2-wire Serial And Analog Interfaces
• Manufacturer: austriamicrosystems

AS5046 Programmable 360° Magnetic Angle Encoder – Preliminary Data Sheet
15.1 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 22:
Figure 22: Defined IC center and magnet displacement radius
15.1.1
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 22). 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 14: Alignment Mode).
The vertical distance should be chosen such that the
magnetic field on the die surface is within the specified
limits (see Figure 21). The typical distance “z” between
the magnet and the package surface is 0.5mm to 1.8mm
with the recommended magnet (6mm x 3mm). 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 MagRngn (pin 1), which will be pulled
low. At this condition, the angular data is still available
over the digital serial interface, but the analog output will
be turned off.
Figure 23: Vertical placement of the magnet
Revision 1.0
Die surface
2.433 mm
2.433 mm
Magnet Placement
N
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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16 Simulation Modeling
Figure 24: Arrangement of Hall sensor array on chip (principle)
With reference to Figure 24, a diametrically magnetized
permanent magnet is placed above or below the surface
of the AS5046. The chip uses an array of Hall sensors to
sample the vertical vector of a magnetic field distributed
across the device package surface. The area of magnetic
sensitivity is a circular locus of 1.1mm radius with
respect to the center of the die. The Hall sensors in the
area of magnetic sensitivity are grouped and configured
such that orthogonally related components of the
magnetic fields are sampled differentially.
the magnetic field. The differential signal X1-X2 will give
an orthogonally related cosine vector of the magnetic
field.
The angular displacement (Θ) of the magnetic source
with reference to the Hall sensor array may then be
modelled by:
The ±0.5° angular error assumes a magnet optimally
aligned over the center of the die and is a result of gain
mismatch errors of the AS5046. Placement tolerances of
the die within the package are ±0.235mm in X and Y
direction, using a reference point of the edge of pin #1
(Figure 24)
In order to neglect the influence of external disturbing
magnetic fields, a robust differential sampling and
ratiometric calculation algorithm has been implemented.
The differential sampling of the sine and cosine vectors
removes any common mode error due to DC components
Θ
The differential signal Y1-Y2 will give a sine vector of
2.433
±0.235mm
=
arctan
AS5046 die
mm
(
(
X
Y
1
1
−
−
Radius of circular Hall sensor
array: 1.1mm radius
1
Y
X
3.9 mm ±0.235mm
2
2
)
)
±
0
5 .
X1
°
Y1
Y2
Center of die
X2
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