AS5040(2004) 데이터 시트보기 (PDF) - austriamicrosystems AG

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AS5040
(Rev.:2004)

10 BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER

austriamicrosystems AG 

AS5040 10-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER

Data D0:D0 is valid, when the status bits have the following

configurations:

OCF COF LIN

Mag

INC

Mag

DEC

Parity

0

0

1

0

0

0

1

even checksum of

bits 1:13

1

0

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

angle:

( ) Position

=

ton ⋅1025

ton + toff

−1

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.

Angle

0 deg

(Pos 0)

PWMIN

1µs

359,65 deg

(Pos 1023)

PWMAX

1/fPWM ± 5%

1025µs

1024µs

Figure 5: PWM output signal

Parameter Symbol Typ Unit

Note

PWM frequency

MIN pulse width

MAX pulse width

fPWM

PWMIN

PWMAX

0.9756

1

1024

kHz Signal period: 1025 µs

- Position 0d

µs

- 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.

Incremental Outputs

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

rotation.

Revision 1.1

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