as5040 austriamicrosystems, as5040 Datasheet - Page 12

• Manufacturer Part Number: as5040
• Description: 10-bit Programmable Magnetic Rotary Encoder
• Manufacturer: austriamicrosystems

AS5040 10-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER
6.2.1
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 = high or open at power-up:
6.3
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
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.
Revision 1.8
CSn has an internal pull-up resistor and must be
externally pulled low (R
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.
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
Incremental Power-up Lock Option
„x+3“ to „x+4“, the incremental output would
ext
≤ 5kΩ). If Csn is low at
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7
The AS5040 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.
Angle
0 deg
(Pos 0)
359.65 deg
(Pos 1023)
Position
Incremental
Output
Indication
Pulse Width Modulation (PWM)
Output
Figure 9: Hysteresis window for incremental outputs
=
X +4
X +3
X +2
X +1
X
(
t
t
on
on
1µs
PW
Figure 10: PWM output signal
X
⋅
+
1025
Counterclockwise Direction
t
X +1
MIN
off
Clockwise Direction
)
X +2
−
Hysteresis:
1
0.7°
X +3
1/f
X +4 X +5
PWM
PW
MAX
1024µs
Page 12 of 27
1025µs
Magnet Position