as5304 austriamicrosystems, as5304 Datasheet - Page 5

• Manufacturer Part Number: as5304
• Description: Integrated Hall Ics For Linear And Off-axis Rotary Motion Detection
• Manufacturer: austriamicrosystems

AS5304/AS5306 Integrated Hall IC for linear and off-axis rotary motion detection
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The digital output is compatible to optical incremental
encoder outputs. Direction of rotation is encoded into
two signals A and B that are phase-shifted by 90º.
Depending on the direction of rotation, A leads B (CW)
or B leads A (CCW).
7.1.1
A single index pulse is generated once for every pole
pair. One pole pair is interpolated to 40 quadrature
pulses (160 steps), so one index pulse is generated
after every 40 quadrature pulses.
7.1.2
The AS5304 can also provide a low magnetic field
warning to indicate a missing magnet or when the end of
the magnetic strip has been reached. This condition is
indicated by using a combination of A,B and Index, that
does not occur in normal operation:
A low magnetic field is indicated with:
Index = high
A=B=low
7.1.3
When using long multipole 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 / 06 provides 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:
Revision 1.0
1.
2.
3.
Incremental Quadrature AB Output
Index Pulse
Magnetic field warning indicator
Soft stop feature for linear movement measurement
First the AS5304/06 moves to the end of the strip, until a magnetic field warning is displayed (Index = high, A=B=low)
Then, the AS5304/06 moves 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 AS5304/06 is reduced
as long as the multipole strip does not fully cover the Hall array.
It is therefore recommended to continue to the next (second) index position from the end of the strip (Index = high,
A=B= high). This position can now be used as a defined home position.
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Index
Detail:
Step #
Index
A
B
A
B
157
S
40
40
158 159
1
1
N
0
2
1
2
2
Figure 6: Quadrature A / B and Index outputs
3
4
S
5
40
40
1
1
N
2
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S