AS5145-HSST austriamicrosystems, AS5145-HSST Datasheet - Page 27

• Manufacturer Part Number: AS5145-HSST
• Description: IC ENCODER PROG 12-BIT 16-SSOP
• Manufacturer: austriamicrosystems
• Type: Linear, Rotary Encoder - Programmabler

Specifications of AS5145-HSST

• Sensing Range: 45mT ~ 75mT
• Voltage - Supply: 3 V ~ 3.6 V, 4.5 V ~ 5.5 V
• Current - Supply: 21mA
• Current - Output (max): 4mA
• Output Type: Quadrature with Index (Incremental)
• Features: Programmable
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AS5145
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
The angular displacement (Q) of the magnetic source with reference to the Hall sensor array may then be modelled by:
The ±0.5º angular error assumes a magnet optimally aligned over the center of the die and is a result of gain mismatch errors of the AS5145.
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
21).
In order to neglect the influence of external disturbing magnetic fields, a robust differential sampling and ratio metric calculation algorithm has
been implemented. 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 ratio metric 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(X1-X2), B(Y1-Y2)) is ±75mT at the 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.
9.6 Failure Diagnostics
The AS5145 also offers several diagnostic and failure detection features:
9.6.1 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: Pins #1 (MagINCn) and #2 (MagDECn) are open-drain outputs and will both be turned on (= low with external pull-up resistor)
when the magnetic field is out of range. If only one of the outputs are low, the magnet is either moving towards the chip (MagINCn) or away from
the chip (MagDECn).
9.6.2 Power Supply Failure Detection
By software: If the power supply to the AS5145 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 DIO and VSS at the receiving side.
By hardware: The MagINCn and MagDECn pins are open drain outputs and require external pull-up resistors. In normal operation, these pins
are high ohmic and the outputs are high
missing, these outputs will become low. To ensure adequate low levels in case of a broken power supply to the AS5145, the pull-up resistors
(~10kΩ) from each pin must be connected to the positive supply at pin 16 (V
By hardware: PWM output: The PWM output is a constant stream of pulses with 1kHz repetition frequency. In case of power loss, these pulses
are missing.
9.7 Angular Output Tolerances
9.7.1 Accuracy
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 = (Errmax – Errmin)/2 is specified as better than ±0.5 degrees @ 25ºC
Figure
Misalignment of the magnet further reduces the accuracy.
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 2x2mm (79x79mil) with a
step size of 100µm.
For each misalignment step, the measurement as shown in
(Errmax – Errmin)/2 (e.g. 0.25º in
www.austriamicrosystems.com/AS5145
- The non-linearity of the analog-digital converters
- Internal gain and mismatch errors
- Non-linearity due to misalignment of the magnet
23).
Figure
(see Table
23) is entered as the Z-axis in the 3D-graph.
9). In a failure case, either when the magnetic field is out of range of the power supply is
Θ
= arctan
Figure 22
Figure 23
------------------------
(
(
X1 X2
Y1 Y2
Revision 1.11
shows an example of a 3D-graph displaying non-linearity over XY-
–
–
is repeated and the accuracy
)
)
DD
± 0.5º
5V).
(see Figure
(see
(EQ 3)
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