AS5040

Data Sheet

www.austriamicrosystems.com

Revision 2.10

13 - 33

Figure 8: Incremental Output Modes

Counterclockwise ccw

A

B

Step / Dir-Mode

Quad A/B-Mode

Index=0

1LSB

Index=1

3 LSB

Index

Mechanical

Zero Position

LSB

Dir

Rotation Direction

Change

CSn

Hyst =

2 LSB

Clockwise cw

Mechanical

Zero Position

Incremental Power-up Lock Option

After power-up, the incremental outputs can optionally be locked or unlocked, depending on the status of the CSn pin:

CSn = low at power-up:

the incremental outputs (A, B, Index) will be high until the internal offset compensation is finished.

This unique state (A=B=Index = high) may be used as an indicator for the external controller to shorten the

waiting time at power-up. Instead of waiting for the specified maximum power up-time (0), the controller can

start requesting data from the AS5040 as soon as the state (A=B=Index = high) is cleared.

CSn = high or open at power-up:

In this mode, the incremental outputs (A, B, Index) will remain at logic high state, until CSn goes low or a low

pulse is applied at CSn. This mode allows intentional disabling of the incremental outputs until for example the

system microcontroller is ready to receive data.

Incremental Output Hysteresis

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

In case of a rotational direction change, the incremental outputs have a hysteresis of 2 LSB.

Regardless of the programmed incremental resolution, the hysteresis of 2 LSB always corresponds to the highest

resolution of 10 bit. In absolute terms, the hysteresis is set to 0.704 degrees for all resolutions.

For constant rotational directions, every magnet position change is indicated at the incremental outputs (see

Figure 9). If for example the magnet turns clockwise from position „x+3“ to „x+4“, the incremental output would also

indicate this position accordingly.

A change of the magnet’s rotational 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 direction, the incremental outputs

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