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Data Sheet - D e t a i l e d D e s c r i p t i o n
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: CSn has an internal pull-up resistor and must be externally pulled low (
). If Csn is 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 AS5140H 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.
7.2.3 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). For example, if 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.
Figure 9. Hysteresis Window for Incremental Outputs
7.3 Pulse Width Modulation (PWM) Output
The AS5140H provides a pulse width modulated output (PWM), whose duty cycle is proportional to the measured angle:
The PWM frequency is internally trimmed to an accuracy of ±5% (±10% over full temperature range). This tolerance can be cancelled by
measuring the complete duty cycle as shown above.