AS5030 8-bit Programmable Magnetic Rotary Encoder

Rev. 1.8

www.austriamicrosystems.com

Page 28 of 33

-1000

-750

-500

-250

0

250

500

750

1000

-1000

-750

-500

-250

0

250

500

750

1000

0,000

0,500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

INL [°]

X Displacement [µm]

Y Displacem ent [µm ]

INL vs. Displacement: AS5030 for AGC24

4,500-5,000

4,000-4,500

3,500-4,000

3,000-3,500

2,500-3,000

2,000-2,500

1,500-2,000

1,000-1,500

0,500-1,000

0,000-0,500

Figure 34: Typical error curve of INL error over lateral displacement (including quantization error)

10.3 Magnet size

Figure 32 to Figure 34 in this chapter describe a cylindrical magnet with a diameter of 6mm. Smaller magnets may also be used,

but since the poles are closer together, the linear range will also be smaller and consequently the tolerance for lateral

misalignment will also be smaller.

If the ± 0.25mm lateral misalignment radius (rotation axis to IC package center) is too tight, a larger magnet can be used.

Larger magnets have a larger linear range and allow more misalignment. However at the same time the slope of the magnet is

more flat which results in a lower differential amplitude.

This requires either a stronger magnet or a smaller gap between IC and magnet in order to operate in the amplitude-controlled

area (AGC > 0 and AGC < 63).

In any case, if a magnet other than the recommended 6mm diameter magnet is used, two parameters should be verified:

•

Verify that the magnetic field produces a sinusoidal wave, when the magnet is rotated.

Note: this can be done with the SIN-/COS- outputs of the AS5030, e.g. rotate the magnet at constant speed and

analyze the SIN- (or COS-) output with an FFT-analyzer.

It is recommended to disable the AGC for this test (see 4.20).

•

the magnet supplier(s).

the magnet (as in Figure 32 or Figure 33)

Furthermore; the sinewave tests described above may be re-run at defined X-and Y- misplacements of the magnet to

determine the maximum acceptable lateral displacement range.

It is recommended to disable the AGC for both these tests (see 4.20).

Note: for preferred magnet suppliers, please refer to the austriamicrosystems website (Rotary Encoder section).