AS5035 – 64 PPR INCREMENTAL MAGNETIC ROTARY ENCODER

Revision 1.5

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Page 9 of 17

For each misalignment step, the measurement as shown

in Figure 14 is repeated and the accuracy

the Z-axis in the 3D-graph.

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.

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 these measurement was a

cylindrical NdFeB (Bomatec® BMN-35H) magnet with

6mm

diameter

and

2.5mm

in

height.

Figure 14: Example of linearity error over 360°

10.2 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

This is the repeatability of an indicated angle at a given

mechanical position.

The transition noise influences the period, width and

phase shift of the output signals A, B and Index:

Parameter

Tolerance (1

σ)

(rms)

Tolerance (3

σ)

(peak)

Index Pulse

width

1.406° +/-0.06°

1.406° +/-0.18°

A,B Pulse width

2.813° +/-0.06°

2.813° +/-0.18°

Period

5.625° +/-0.06°

5.625° +/-0.18°

A-B Phase shift

90e° +/-1.9e°

90e° +/-5.7e°

Table 3: Incremental signal tolerances with transition noise

e° = electrical degrees (see Figure 5)

*1

: statistically, 1 sigma represents 68.27% of readings,

3 sigma represents 99.73% of readings.

The algorithm used to generate the incremental outputs

guarantees no missing or additional pulses even at high

speeds (up to 30,000 rpm and higher)

10.3 High Speed Operation

10.3.1

Sampling Rate

The AS5035 samples the angular value at a rate of 10k

samples per second. Consequently, the incremental

outputs are updated each 100µs.

At a stationary position of the magnet, this sampling rate

creates no additional error.

Incremental encoders are usually required to produce no

missing pulses up to several thousand rpm’s.

Therefore, the AS5035 has a built-in interpolator, which

ensures that there are no missing pulses at the

incremental outputs for rotational speeds of up to

10,000rpm.

linearity error with centered magnet [degrees]

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0

°

90°

180°

270°

360°

transition noise