AS5046ASST datasheet(28/33 Pages) AMSCO

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AS5046 Programmable 360° Magnetic Angle Encoder – Preliminary Data Sheet

Revision 1.1

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Page 28 of 33

15.1 Physical Placement of the Magnet

The best linearity can be achieved by placing the center

of the magnet exactly over the defined center of the IC

package as shown in Figure 22:

Defined

center

2.433 mm

3.9 mm

Area of recommended maximum

magnet misalignment

Figure 22: Defined IC center and magnet displacement radius

15.1.1 Magnet Placement

The magnet’s center axis should be aligned within a

displacement radius Rd of 0.25mm from the defined

center of the IC with reference to the edge of pin #1 (see

Figure 22). This radius includes the placement tolerance

of the chip within the SSOP-16 package (+/- 0.235mm).

The displacement radius Rd is 0.485mm with reference to

the center of the chip (see section 14: Alignment Mode).

The vertical distance should be chosen such that the

magnetic field on the die surface is within the specified

limits (see Figure 21). The typical distance “z” between

the magnet and the package surface is 0.5mm to 1.8mm

with the recommended magnet (6mm x 3mm). Larger

gaps are possible, as long as the required magnetic field

strength stays within the defined limits.

A magnetic field outside the specified range may still

produce usable results, but the out-of-range condition

will be indicated by MagRngn (pin 1), which will be pulled

low. At this condition, the angular data is still available

over the digital serial interface, but the analog output will

be turned off.

1.282mm ± 0.15mm

0.576mm ± 0.1mm

Package surface

Die surface

Figure 23: Vertical placement of the magnet

16 Simulation Modeling

Figure 24: Arrangement of Hall sensor array on chip (principle)

With reference to Figure 24, a diametrically magnetized

permanent magnet is placed above or below the surface

of the AS5046. The chip uses an array of Hall sensors to

sample the vertical vector of a magnetic field distributed

across the device package surface. The area of magnetic

sensitivity is a circular locus of 1.1mm radius with

respect to the center of the die. The Hall sensors in the

area of magnetic sensitivity are grouped and configured

such that orthogonally related components of the

magnetic fields are sampled differentially.

The differential signal Y1-Y2 will give a sine vector of

the magnetic field. The differential signal X1-X2 will give

an orthogonally related cosine vector of the magnetic

field.

The angular displacement (

Θ) of the magnetic source

with reference to the Hall sensor array may then be

modelled by:

(

)

()

−

arctan

The

±0.5° angular error assumes a magnet optimally

aligned over the center of the die and is a result of gain

mismatch errors of the AS5046. Placement tolerances of

the die within the package are

±0.235mm in X and Y

direction, using a reference point of the edge of pin #1

(Figure 24)

In order to neglect the influence of external disturbing

magnetic fields, a robust differential sampling and

ratiometric calculation algorithm has been implemented.

The differential sampling of the sine and cosine vectors

removes any common mode error due to DC components

AS5046 die

Radius of circular Hall sensor

array: 1.1mm radius

Center of die

2.433

±0.235mm

3.9 mm

±0.235mm

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