AS5304/AS5306 Integrated Hall IC for linear and off-axis rotary motion detection

Revision 1.5

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3.0475±0.235

Hall Array Center Line

Magnet drawn at

index position X=0

CW magnet

movement direction

Pin 1

Chip Top view

3.0475±0.235

Hall Array Center Line

Magnet drawn at

position X1

(exaggerated)

CW magnet

movement direction

Pin 1

Chip Top view

X

X

25µm (AS5304)

15µm (AS5306)

Index = High

Index = Low

N

S

N

S

Figure 7:

Magnet placement for index pulse generation

7.1.4

Soft Stop Feature for Linear Movement Measurement

When using long multi-pole strips, it may often be necessary to start from a defined home (or zero) position and obtain absolute

position information by counting the steps from the defined home position. The AS5304/AS5306 provide a soft stop feature that

eliminates the need for a separate electro-mechanical home position switch or an optical light barrier switch to indicate the

home position.

The magnetic field warning indicator (see 7.1.2) together with the index pulse can be used to indicate a unique home position

on a magnetic strip:

1.

First the AS5304/AS5306 move to the end of the strip, until a magnetic field warning is displayed (Index = high,

A=B=low)

2.

Then, the AS5304/AS5306 move back towards the strip until the first index position is reached (note: an index position

is generated once for every pole pair, it is indicated with: Index = high, A=B= high). Depending on the polarity of the

strip magnet, the first index position may be generated when the end of the magnet strip only covers one half of the

Hall array. This position is not recommended as a defined home position, as the accuracy of the AS5304/AS5306 are

reduced as long as the multi-pole strip does not fully cover the Hall array.