AS5046ASST datasheet(27/33 Pages) AMSCO

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AS5046 Programmable 360° Magnetic Angle Encoder – Preliminary Data Sheet

Revision 1.1

www.austriamicrosystems.com

Page 27 of 33

14 Alignment Mode

The alignment mode simplifies centering the magnet over

the chip to gain maximum accuracy and XY-alignment

tolerance.

This electrical centering method allows a wider XY-

alignment tolerance (0.485mm radius) than mechanical

centering (0.25mm radius) as it eliminates the placement

tolerance of the die within the IC package (+/- 0.235mm).

Alignment mode can be enabled with the falling edge of

CSn while PROG = logic high (Figure 19). The Data bits

D11-D0 of the serial interface change to a 12-bit

displacement amplitude output. A high value indicates

large X or Y displacement, but also higher absolute

magnetic field strength. The magnet is properly aligned,

when the difference between highest and lowest value

over one full turn is at a minimum.

Under normal conditions, a properly aligned magnet will

result in a reading of less than 128 over a full turn.

Stronger magnets or short gaps between magnet and IC

may show values larger than 128. These magnets are

still properly aligned as long as the difference between

highest and lowest value over one full turn is at a

minimum.

The MagInc and MagDec indicators will be = 1 when the

alignment mode reading is < 128. At the same time,

hardware pin MagRngn (#1) will be pulled to VSS.

The Alignment mode can be reset to normal operation

mode by a power-on-reset (cycle power supply) or by a

falling edge of CSn with PROG=low (see Figure 20).

Figure 19: Enabling the alignment mode

Figure 20: Exiting alignment mode

15 Choosing the Proper Magnet

Typically the magnet should be 6mm in diameter and ≥2.5mm in

height. Magnetic materials such as rare earth AlNiCo, SmCo5 or

NdFeB are recommended.

The magnet’s field strength perpendicular to the die

surface should be verified using a gauss-meter. The

magnetic field Bv at a given distance, along a concentric

circle with a radius of 1.1mm (R1), should be in the range

of ±45mT…±75mT. (see Figure 21).

Magnet axis

Vertical field

component

(45…75mT)

360

Vertical field

component

R1 concentric circle;

radius 1.1mm

Magnet axis

typ. 6mm diameter

Figure 21: Typical magnet and magnetic field distribution

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