AS5035-T View Datasheet(PDF) - austriamicrosystems AG
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AS5035-T Datasheet PDF : 18 Pages
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AS5035 – 64 PPR INCREMENTAL MAGNETIC ROTARY ENCODER
8 Simulation Modelling
3.9 mm ±0.235mm
1
removes any common mode error due to DC components
introduced by the magnetic source itself or external
disturbing magnetic fields. A ratiometric division of the
sine and cosine vectors removes the need for an
accurate absolute magnitude of the magnetic field and
thus accurate Z-axis alignment of the magnetic source.
The recommended differential input range of the
2.433 mm
Y1
magnetic field strength (B(X1-X2),B(Y1-Y2)) is ±75mT at the
±0.235mm
surface of the die. In addition to this range, an additional
X1
X2
lid Y2
va AS5040 die
Center of die
ill Radius of circular Hall sensor
array: 1.1mm radius
t Figure 9: Arrangement of Hall sensor array on chip (principle)
G s With reference to Figure 9, a diametrically magnetized
permanent magnet is placed above or below the surface
A t of the AS5035. The chip uses an array of Hall sensors to
sample the vertical vector of a magnetic field distributed
s n across the device package surface. The area of magnetic
e sensitivity is a circular locus of 1.1mm radius with
m t respect to the center of the die. The Hall sensors in the
area of magnetic sensitivity are grouped and configured
a n such that orthogonally related components of the
magnetic fields are sampled differentially.
o The differential signal Y1-Y2 will give a sine vector of
c the magnetic field. The differential signal X1-X2 will give
an orthogonally related cosine vector of the magnetic
l field.
a The angular displacement (Θ) of the magnetic source
with reference to the Hall sensor array may then be
ic modelled by:
n Θ
=
arctan
(Y
(X
1
1
−
−
Y 2)
X 2)
±
0.5°
h The ±0.5° angular error assumes a magnet optimally
aligned over the center of the die and is a result of gain
c mismatch errors of the AS5035. Placement tolerances of
the die within the package are ±0.235mm in X and Y
e direction, using a reference point of the edge of pin #1
T(Figure 11)
offset of ±5mT, caused by unwanted external stray fields
is allowed.
The chip will continue to operate, but with degraded
output linearity, if the signal field strength is outside the
recommended range. Too strong magnetic fields will
introduce errors due to saturation effects in the internal
preamplifiers. Too weak magnetic fields will introduce
errors due to noise becoming more dominant.
9 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.
typ. 6mm diameter
N
R1
Vertical field
component
S
Magnet axis
Magnet axis
Vertical field
component
Bv
R1 concentric circle;
radius 1.1mm
(45…75mT)
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
0
360
360
Figure 10: Typical magnet and magnetic field distribution
Revision 1.5
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