www.austriamicrosystems.com/AS5130

Revision 1.12

32 - 41

AS5130

Datasheet - Application In form atio n

8.4.2 Vertical Distance of the Magnet

The chip-internal automatic gain control (AGC) regulates the input signal amplitude for the tracking-ADC to a constant value. This improves the

accuracy of the encoder and enhances the tolerance for the vertical distance of the magnet.

Figure 27. Typical Curves for Vertical Distance versus ACG Value on Several Untrimmed Samples

As shown in Figure 27, the AGC value (left Y-axis) increases with vertical distance of the magnet. Consequently, it is a good indicator for

determining the vertical position of the magnet, for example as a pushbutton feature, as an indicator for a defective magnet or as a preventive

warning (e.g. for wear on a ball bearing etc.) when the nominal AGC value drifts away. If the magnet is too close or the magnetic field is too

strong, the AGC will be reading 0. If the magnet is too far away (or missing) or if the magnetic field is too weak, the AGC will be reading 63 (3FH).

The AS5130 will still operate outside the AGC range, but the accuracy may be reduced as the signal amplitude can no longer be kept at a

constant level. The linearity curve in Figure 27 (right Y-axis) shows that the accuracy of the AS5130 is best within the AGC range, even slightly

better at small airgaps (0.4 – 0.8mm). At very short distances (0 – 0.1) the accuracy is reduced, mainly due to nonlinearities in the magnetic field.

At larger distances, outside the AGC range (~2.0 – 2.5mm and more) the accuracy is still very good, only slightly decreased from the nominal

accuracy. Since the field strength of a magnet changes with temperature, the AGC will also change when the temperature of the magnet

changes. At low temperatures, the magnetic field will be stronger and the AGC value will decrease. At elevated temperatures, the magnetic field

will be weaker and the AGC value will increase.

Linearity and AGC vs Airgap

0

8

16

24

32

40

48

56

64

0

500

1000

1500

2000

2500

Airgap [µm]

1,0

1,2

1,4

1,6

1,8

2,0

2,2

sample#1

sample#2

sample#3

sample#4

Linearity [°]