|AS5040||10 BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER|
|AS5040 Datasheet PDF : 20 Pages |
AS5040 10-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER
Data D0:D0 is valid, when the status bits have the following
OCF COF LIN
even checksum of
Table 4: status bit outputs
The absolute angular position is sampled at a rate of 10 kHz
(0.1ms). This allows reading out all 1024 positions per 360
degrees within 0.1 seconds (9.76 Hz) without skipping any
position. By multiplying 10Hz by 60, one obtains the
corresponding maximum rotational speed of 585.9 rpm.
If skipping every second absolute angular position would be
acceptable for specific applications, one could increase the
rotational speed of the magnet source by a factor of two.
Thus speeds of 1200 rpm would be achievable.
Readout of every absolute angular position allows for
rotational speeds of up to 600rpm
Readout of every second angular position allows for
rotational speeds of up to 1200rpm
Consequently increasing the rotational speed diminishes the
number of absolute angular positions to be read out (see
Table 6). Regardless of the rotational speed or the number
of positions to be read out, the absolute angular value is
always given at the highest resolution of 10-bit.
The incremental outputs are not affected by rotational
speed restrictions due to the implemented interpolator. The
incremental output signals may be used for high-speed
applications with rotational speeds of up to 10,000rpm
without missing pulses.
10bit Pulse Width Modulation Output
The AS5040 provides a pulse width modulated output
(PWM), whose duty cycle is proportional to the measured
( ) Position
ton + toff
The PWM frequency is internally trimmed to an accuracy of
±5%. This tolerance can be cancelled by measuring the
complete duty cycle as shown above.
1/fPWM ± 5%
Figure 5: PWM output signal
Parameter Symbol Typ Unit
MIN pulse width
MAX pulse width
kHz Signal period: 1025 µs
- Position 0d
- Angle 0 deg
- Position 1023d
µs - Angle 359,65 deg
Table 5: PWM signal parameters
Generating an Analog Output
This can be achieved by averaging the PWM signal, using
an external active or passive low pass filter.
This method generates an analogue output signal that is
proportional to the measured angle. Thus the device can be
used as direct replacement of potentiometers with an
analogue voltage output.
Three different incremental output modes are possible with
Quadrature A/B being the default mode.
Figure 6 shows the two-channel quadrature as well as the
single channel incremental signal (LSB) and the direction bit
in clockwise (CW) and counter-clockwise (CCW) direction.
Quadrature A / B Output (quad AB Mode)
The phase shift between channel A and B indicates the
direction of the magnet movement. Channel A leads channel
B at a clockwise rotation of the magnet (top view, magnet
placed above or below the device) with 90 electrical
degrees. Channel B leads channel A at a counter-clockwise
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