AS5035 austriamicrosystems, AS5035 Datasheet - Page 7

• Manufacturer Part Number: AS5035
• Description: IC, MAGNETIC ROTARY ENCODER 8BIT SSOP-16
• Manufacturer: austriamicrosystems
• Type: Magnetic Rotary Encoderr

Specifications of AS5035

• Ic Function: Encoder IC
• Supply Voltage Range: 3.3V, 5V
• Operating Temperature Range: -40°C To +125°C
• Digital Ic Case Style: SSOP
• No. Of Pins: 16
• Filter Terminals: SMD
• No. Of Bits: 8 Bit
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AS5035 – 64 PPR INCREMENTAL MAGNETIC ROTARY ENCODER
8
With reference to Figure 9, a diametrically magnetized
permanent magnet is placed above or below the surface
of the AS5035. 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 AS5035. 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 11)
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
Revision 1.5
Θ
The differential signal Y1-Y2 will give a sine vector of
Figure 9: Arrangement of Hall sensor array on chip (principle)
± 0.235mm
=
2.433 mm
arctan
Simulation Modelling
AS5040 die
(
(
X
Y
1
1
−
−
Radius of circular Hall sensor
array: 1.1mm radius
Y
1
X
3.9 mm ± 0.235mm
2
2
)
)
±
0
5 .
X1
°
Y1
Y2
Center of die
X2
www.austriamicrosystems.com
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
magnetic field strength (B
surface of the die. In addition to this range, an additional
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
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.
Figure 10: Typical magnet and magnetic field distribution
Choosing the Proper Magnet
Vertical field
component
Vertical field
component
Bv
0
360
N
(45…75mT)
(X1-X2)
R1
,B
typ. 6mm diameter
(Y1-Y2)
R1 concentric circle;
radius 1.1mm
S
Magnet axis
) is ± 75mT at the
Magnet axis
360
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