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

Revision 1.5

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7 Incremental Quadrature AB Output

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

Index Pulse

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 (see Figure 6)

The Index output is switched to Index = high, when a

magnet is placed over the Hall array as shown in

Figure 7, top graph: the north pole of the magnet is

placed over the left side of the IC (top view, pin#1 at

bottom left) and the south pole is placed over the

right side of the IC.

The index output will switch back to Index = low,

when the magnet is moved by one LSB from position

X=0 to X=X1, as shown in Figure 7, bottom graph.

One LSB is 25µm for AS5304 and 15µm for AS5306.

Note: Since the small step size of 1 LSB is hardly

recognizable in a correctly scaled graph it is shown as an

exaggerated step in the bottom graph of Figure 7.

Figure 6:

Quadrature A / B and Index output

7.1.2

Magnetic Field Warning Indicator

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

Vertical Distance between Magnet and IC

The recommended vertical distance between magnet and IC depends on the strength of the magnet and the length of the

magnetic pole.

Typically, the vertical distance between magnet and chip surface should not exceed ½ of the pole length.

That means for AS5304, having a pole length of 2.0mm, the maximum vertical gap should be 1.0mm,

For the AS5306, having a pole length of 1.2mm, the maximum vertical gap should be 0.6mm

These figures refer to the chip surface. Given a typical distance of 0.2mm between chip surface and IC package surface,

the recommended vertical distances between magnet and IC surface are therefore:

AS 5304: ≤ 0.8mm

AS 5306: ≤ 0.4mm

N

40

1

2

A

40

1

2

40

1

2

B

40

1

2

Index

S

S

NS

A

157

B

Index

Detail:

Step #

158 159

0

1

2

3

4

5