AS5311

Data Sheet

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Revision 1.01

12 - 23

7.2

Incremental Output Hysteresis

Figure 7: Hysteresis Illustration

Magnet Position

Hysteresis:

2 steps

X +2

Incremental

Output

Indication

Movement left -> right

Movement right -> left

X +4

X

X

X+2

X+4 X+5

X+3

X+1

X +1

X +3

To avoid flickering incremental outputs at a stationary magnet position, a hysteresis is introduced.

In case of a movement direction change, the incremental outputs have a hysteresis of 2 LSB. For constant

movement directions, every magnet position change is indicated at the incremental outputs (see Figure 6). If for

example the magnet moves from position „x+3“ to „x+4“, the incremental output would also indicate this position

accordingly.

A change of the magnet’s movement direction back to position „x+3“ means, that the incremental output still

remains unchanged for the duration of 2 LSB, until position „x+2“ is reached. Following this movement, the

incremental outputs will again be updated with every change of the magnet position.

7.3

Synchronous Serial Interface (SSI)

The Serial interface allows data transmission of the 12-bit absolute linear position information (within one pole

pair = 2.0mm). Data bits D11:D0 represent the position information with a resolution of 488nm (2000µm / 4096)

per step.

CLK must be high at the falling edge of CSn.

Figure 8: Synchronous Serial Interface with Absolute Angular Position Data

D11

1

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

OCF COF

LIN

Mag

INC

Mag

DEC

Even

PAR

D11

1

18

8

t

CLK FE

t

CSn

t

DO Tristate

Status Bits

Angular Position Data

t

DO valid

t

DO active

T

CLK/2

t

CLK FE

CSn

DO

CLK

If CLK is low at the falling edge of CSn, the first 12 bits represent the magnitude information, which is

proportional to the magnetic field strength. This information can be used to detect the presence and proper

distance of the magnetic strip by comparing it to a known good value (depends on the magnet material and

distance).

The automatic gain control (AGC) maintains a constant MAGnitude value of 3F hex (=”green” range). If the MAG

value is <>3F hex, the AGC is out of the regulating range (“yellow” or “red” range). See Table 5 for more details.