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AS5311

Datasheet - A pp l ic a t io n I n f or m a t i on

8.3 Mounting the Magnet

8.3.1 Vertical Distance

As a rule of thumb, the gap between chip and magnet should be ½ of the pole length, that is Z=0.5mm for the 1.0mm pole length of the AS5311

magnets. However, the gap also depends on the strength of the magnet. Typical gaps for AS5311 magnets range from 0.3 to 0.6mm (see

Electrical System Specifications on page 8).

The AS5311 automatically adjusts for fluctuating magnet strength by using an automatic gain control (AGC). The vertical distance should be set

such that the AS5311 is in the “green” range. See Z-axis Range Indication (“Red/Yellow/Green” Indicator) on page 14 for more details.

8.3.2 Alignment of Multi-pole Magnet and IC

When aligning the magnet strip or ring to the AS5311, the centerline of the magnet strip should be placed exactly over the Hall array. A lateral

displacement in Y-direction (across the width of the magnet) is acceptable as long as it is within the active area of the magnet. See Figure 14 for

the position of the Hall array relative to Pin #1.

Note:

The active area in width is the area in which the magnetic field strength across the width of the magnet is constant with reference to the

centerline of the magnet (see Figure 13).

8.3.3 Lateral Stroke of Multi-pole Strip Magnets

The lateral movement range (stroke) is limited by the area at which all Hall sensors of the IC are covered by the magnet in either direction. The

Hall array on the AS5311 has a length of 2.0mm, hence the total stroke is,

maximum lateral Stroke = Length of active area – length of Hall array

(EQ 2)

Note:

Active area in length is defined as the area containing poles with the specified 1.0mm pole length. Shorter poles at either edge of the

magnet must be excluded from the active area (see Figure 13).

Figure 13. Active Area of Strip Magnet

N

strip length

2mm

S

N

S

N

S

N

S

N

S

Active area ( length )

Active Area

recommended

scanning path

B