AS5040-ASST View Datasheet(PDF) - austriamicrosystems AG

Part Name

Description

Manufacturer

AS5040-ASST

10-Bit 360º Programmable Magnetic Rotary Encoder

austriamicrosystems AG 

AS5040 − Angular Output Tolerances

Angular Error Caused by Propagation Delay

A rotating magnet will therefore cause an angular error caused

by the output delay. This error increases linearly with speed:

(EQ8) esampling = rpm × 6 × prop⋅delay

Where:

esampling = angular error [º]

rpm = rotating speed [rpm]

prop delay = propagation delay [seconds]

Note(s): Since the propagation delay is known, it can be

automatically compensated by the control unit processing the

data from the AS5040, thus reducing the angular error caused

by speed.

Internal Timing Tolerance

The AS5040 does not require an external ceramic resonator or

quartz. All internal clock timings for the AS5040 are generated

by an on-chip RC oscillator. This oscillator is factory trimmed to

±5% accuracy at room temperature (±10% over full

temperature range). This tolerance influences the ADC

sampling rate and the pulse width of the PWM output:

• Absolute Output; SSI Interface:

A new angular value is updated every 100μs (typ)

• Incremental outputs:

the incremental outputs are updated every 100μs (typ.)

(EQ9)

• PWM output:

A new angular value is updated every 100μs (typ.).

The PWM pulse timings Ton and Toff also have the same

tolerance as the internal oscillator.

If only the PWM pulse width Ton is used to measure the

angle, the resulting value also has this timing tolerance.

However, this tolerance can be canceled by measuring

both Ton and Toff and calculating the angle from the duty

cycle (see Incremental Outputs):

Position

=

--t--o--n----⋅---1---0---2---5---

(ton + toff)

–

1

ams Datasheet

[v2-12] 2017-Jun-20

Page 49

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