AS5306AATSU austriamicrosystems, AS5306AATSU Datasheet - Page 7

• Manufacturer Part Number: AS5306AATSU
• Description: IC, LINEAR ENCODER, 12.3BIT, 20-TSSOP
• Manufacturer: austriamicrosystems
• Type: Linear Magneticr

Specifications of AS5306AATSU

• Ic Function: Encoder IC
• Supply Voltage Range: 4.5V To 5.5V
• Operating Temperature Range: -40°C To +125°C
• Digital Ic Case Style: TSSOP
• No. Of Pins: 20
• Termination Type: SMD
• Filter Terminals: SMD
• Rohs Compliant: Yes
• Package / Case: 20-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AS5304/AS5306 Integrated Hall IC for linear and off-axis rotary motion detection
7.2
Figure 8:
7.3
The INL (integral non-linearity) is the deviation between indicated position and actual position. It is better than 1LSB for both
AS5304 and AS5306, assuming an ideal magnet. Pole length variations and imperfections of the magnet material, which lead to
a non-sinusoidal magnetic field will attribute to additional linearity errors.
7.3.1
Figure 9:
Figure 10:
Revision 1.5
X + 4
X + 3
X + 2
X + 1
I ncrem en tal
X
3.
140
120
100
140
120
100
o ut put
80
60
40
20
80
60
40
20
0
0
1500
Incremental Hysteresis
Integral Non-Linearity (INL)
900
M ovem ent direc tion: -X
It is therefore recommended to continue to the next (second) index position from the end of the strip (Index = high,
A=B= high). This position can now be used as a defined home position.
Error Caused by Pole Length Variations
X
AS5304 Systematic Linearity Error caused by Pole
AS5306 Systematic Linearity Error caused by Pole
Hysteresis of the incremental output
Additional error caused by pole length variation: AS5304
Additional error caused by pole length variation: AS5306
Mov ement d ir ection: +X
1000
X+1
1700
X+2
1100
Length Deviation
Length Deviation
Pole Length [μm]
Pole Length [μm]
1900
H ys teres is:
1 LS B
X+ 3
1200
M agnet po sition
X+4
2100
1300
Error [µm]
www.austriamicrosystems.com
2300
Error [µm]
1400
If the magnet is sitting right at the transition point between two steps, the
noise in the system may cause the incremental outputs to jitter back and
forth between these two steps, especially when the magnetic field is
weak.
To avoid this unwanted jitter, a hysteresis has been implemented. The
hysteresis lies between 1 and 2 LSB, depending on device scattering.
Figure 8 shows an example of 1LSB hysteresis: the horizontal axis is the
lateral position of the magnet as it scans across the IC, the vertical axis
is the change of the incremental outputs, as they step forward (blue line)
with movement in +X direction and backward (red line) in –X direction.
Note: 1LSB = 25µm for AS5304, 15µm for AS5306
1500
2500
Figure 9 and Figure 10 show the error caused by a non-ideal
pole length of the multi-pole strip or ring.
This is less of an issue with strip magnets, as they can be
manufactured exactly to specification using the proper
magnetization tooling.
However, when using a ring magnet (see Figure 1) the pole
length differs depending on the measurement radius. For
optimum performance it is therefore essential to mount the
IC such that the Hall sensors are exactly underneath the
magnet at the radius where the pole length is 2.0mm
(AS5304) or 1.2mm (AS5306), see also 8.1.2.
Note that this is an additional error, which must be added to
the intrinsic errors INL (see 7.3) and DNL (see 7.4).
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