as5043 austriamicrosystems, as5043 Datasheet - Page 17

• Manufacturer Part Number: as5043
• Description: 10-bit Programmable 360? Magnetic Angle Encoder With Absolute Digital And Analog Outputs
• Manufacturer: austriamicrosystems

AS5043 Programmable 360° Magnetic Angle Encoder
The differential sampling of the sine and cosine vectors
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.
17 Failure Diagnostics
The AS5043 also offers several diagnostic and failure
detection features:
17.1 Magnetic field strength diagnosis
By software: the MagInc and MagDec status bits will
both be high when the magnetic field is out of range.
By hardware: Pin #1 (MagRngn) is a logical NAND-ed
combination of the MagInc and MagDec status bits. It is
an open-drain output and will be turned on (= low with
external pull-up resistor) when the magnetic field is out
of range.
By hardware: Pin #12 (Vout) is the analog output of the
DAC and OP-Amp. The analog output will be 0V, when
the magnetic field is out of range (all analog modes).
17.2 Power supply failure detection
By software: If the power supply to the AS5043 is
interrupted, the digital data read by the SSI will be all
“0”s. Data is only valid, when bit OCF is high, hence a
data stream with all “0”s is invalid. To ensure adequate
low levels in the failure case, a pull-down resistor
(~10kΩ) should be added between pin DO and VSS at
the receiving side
By hardware: The MagRngn pin is an open drain output
and requires an external pull-up resistor. In normal
operation, this pin is high ohmic and the output is high.
In a failure case, either when the magnetic field is out of
range or the power supply is missing, this output will
become low. To ensure an adequate low level in case of
Revision 1.6, 3-Oct-06
(X1-X2)
,B
(Y1-Y2)
) is ±75mT at the
www.austriamicrosystems.com
a broken power supply to the AS5043, the pull-up
resistor (~10kΩ) must be connected to the positive
supply at pin 16 (VDD5V).
.
18 Angular Output tolerances
18.1 Accuracy; digital outputs
Accuracy is defined as the error between measured
angle and actual angle. It is influenced by several
factors:
As a sum of all these errors, the accuracy with centered
magnet = (Err
±0.5 degrees @ 25°C (see Figure 23).
Misalignment
accuracy. Figure 22 shows an example of a 3D-graph
displaying non-linearity over XY-misalignment. The
center of the square XY-area corresponds to a centered
magnet (see dot in the center of the graph). The X- and
Y- axis extends to a misalignment of ±1mm in both
directions. The total misalignment area of the graph
covers a square of 2x2 mm (79x79mil) with a step size of
100µm.
For each misalignment step, the measurement as shown
in Figure 23 is repeated and the accuracy
(Err
the Z-axis in the 3D-graph.
18.2 Accuracy; analog output
The analog output has the same accuracy as the digital
output with the addition of the nonlinearities of the DAC
and the OPAMP (+/-1LSB; see Table 5 and 19.3.5).
Figure 22: Example of linearity error over XY misalignment
max
– Err
6
°
the non-linearity of the analog-digital converters,
internal gain and mismatch errors,
non-linearity due to misalignment of the magnet
5
4
3
2
1
0
min
max
)/2 (e.g. 0.25° in Figure 23) is entered as
of
Linearity Error over XY-misalignment [°]
– Err
the
y
min
magnet
)/2 is specified as better than
further reduces
-1000
-700
-400
-100
200
500
x
800
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