AS5040

Data Sheet

www.austriamicrosystems.com

Revision 2.10

15 - 33

Table 5: PWM Signal Parameters

Parameter

Symbol

Typ

Unit

Note

PWM frequency

0.9756

kHz

Signal period: 1025µs

MIN pulse width

1

µs

- Position 0d

- Angle 0 deg

MAX pulse width

1024

µs

- Position 1023d

- Angle 359,65 deg

10 Analog Output

An analog output may be generated by averaging the PWM signal, using an external active or passive lowpass filter.

The analog output voltage is proportional to the angle: 0°= 0V; 360° = VDD5V.

Using this method, the AS5040 can be used as direct replacement of potentiometers.

Figure 11: Simple Passive 2

R1,R2

≥ 4k7

C1,C2

≥ 1µF / 6V

R1 should be

≥4k7 to avoid loading of the PWM output. Larger values of Rx and Cx will provide better filtering and

less ripple, but will also slow down the response time.

11 Brushless DC Motor Commutation Mode

Brushless DC motors require angular information for stator commutation. The AS5040 provides U-V-W commutation

signals for one and two pole pair motors. In addition to the three-phase output signals, the step (LSB) output at pin 12

allows high accuracy speed measurement. Two resolutions (9 or 10 bit) can be selected by programming Div0

according to Table 6.

Mode 3.0 (3.1) is used for brush-less DC motors with one-pole pair rotors. The three phases (U, V, W) are 120

degrees apart, each phase is 180 degrees on and 180 degrees off.

Mode 3.2 (3.3) is used for motors with two pole pairs requiring a higher pulse count to ensure a proper current

commutation. In this case the pulse width is 256 positions, equal to 90 degrees.

The precise physical angle at which the U, V and W signals change state (“Angle” in Figure 12 and Figure 13) is

calculated by multiplying each transition position by the angular value of 1 count:

Angle [deg] = Position x (360 degree / 1024)

360°

C1

R1

R2

analog out

C2

Pin12

PWM

Pin7

VSS

0°

0V

2

VDD

2