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AS5245

Data Sheet - A p p l i c a t i o n I n f o r m a t i o n

9.5 Failure Diagnostics

The AS5245 also offers several diagnostic and failure detection features, which are discussed in detail further in the document.

9.5.1 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).

9.5.2 Power Supply Failure Detection

By Software: If the power supply to the AS5245 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 (~10k

Ω) 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 (see Table 9). In a failure case, either when the magnetic field is out of range of the power supply is

missing, these outputs will become low. To ensure adequate low levels in case of a broken power supply to the AS5245, the pull-up resistors

(~10k

Ω) from each pin must be connected to the positive supply at pin 16 (VDD5V).

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.

9.6 Angular Output Tolerances

9.6.1 Accuracy

Accuracy is defined as the error between measured angle and actual angle. It is influenced by several factors:

The non-linearity of the analog-digital converters,

Internal gain and mismatch errors,

Non-linearity due to misalignment of the magnet.

Figure 19).

Misalignment of the magnet further reduces the accuracy. Figure 18 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.

entered as the Z-axis in the 3D-graph.