as5046 austriamicrosystems, as5046 Datasheet - Page 30

• 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
The maximum non-linearity error on this example is
better than ±1 degree (inner circle) over a misalignment
radius of ~0.7mm. For volume production, the placement
tolerance of the IC within the package (±0.235mm) must
also be taken into account.
18.3 Transition Noise
Transition noise is defined as the jitter in the transition
between two steps.
Due to the nature of the measurement principle (Hall
sensors + Preamplifier + ADC), there is always a certain
degree of noise involved.
This transition noise voltage results in an angular
transition noise at the outputs. It is specified as 0.06
degrees rms (1 sigma)
and
MODE = low or open).
These values are the repeatability of an indicated angle
at a given mechanical position.
The transition noise has different implications on the type
of output that is used:
Revision 1.0
-0.1
-0.2
-0.3
-0.4
-0.5
0.5
0.4
0.3
0.2
0.1
0
0.03 degrees rms (1 sigma)
1
absolute output; serial interface:
The transition noise of the absolute output can
be reduced by the user by applying an
averaging of readings. An averaging of 4
readings will reduce the transition noise by 6dB
or 50%, e.g. from 0.03°rms to 0.015°rms (1
sigma) in slow mode
analog output:
Ideally, the analog output should have a jitter
that is less than one digit. In 360° mode, both
fast or slow mode may be selected for adequate
low jitter.
55 109 163 217 271 325 379 433 487 541 595 649 703 757 811 865 919 973
*1
in fast mode (pin MODE = high)
linearity
*1
in slow mode (pin
Err max
Figure 26: Example of linearity error over 360°
error
www.austriamicrosystems.com
with
centered
Err min
The total nonlinearity error over process tolerances,
temperature and a misalignment circle radius of 0.25mm
is specified better than ±1.4 degrees.
The magnet used for this measurement was a cylindrical
NdFeB (Bomatec® BMN-35H) magnet with 6mm diameter and
2.5mm in height.
18.4 High Speed Operation
18.4.1
The AS5046 samples the angular value at a rate of
10.42k samples per second (ksps) in fast mode and
2.61ksps in slow mode.
Consequently, a new reading is performed each 96µs.
(fast mode) or 384µs (slow mode).
At a stationary position of the magnet, this sampling rate
creates no additional error.
Absolute Mode:
With the given sampling rates, the number of samples (n)
per turn for a magnet rotating at high speed can be
calculated by
n
n
magnet
=
=
rpm
rpm
60
In 180°, 90° or 45° mode, where the step sizes
are smaller, slow mode should be selected to
reduce the output jitter.
*1
3 sigma represents 99.73% of readings.
Sampling Rate
⋅
60
⋅
: statistically, 1 sigma represents 68.27% of readings,
96
384
transition noise
μ
μ
s
s
for fast mode
for slow mode
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