AS5130ASST datasheet(30/40 Pages) AMSCO

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AS5130

Data Sheet - A p p l i c a t i o n I n f o r m a t i o n

Figure 23. Quantization Error of a Low Resolution and a High Resolution System

The resolution of the encoder determines the smallest step size. The angle error caused by quantization cannot get

better than ± ½ LSB. As shown in Figure 23, a higher resolution system (right picture) has a smaller quantization error,

as the step size is smaller. For the AS5130, the quantization error is ± ½ LSB = ± 0.7º

Figure 24. Typical INL Error over 360º

Figure 24 shows a typical example of an error curve over a full turn of 360º at a given X-Y- displacement. The curve

includes the quantization error, transition noise and the system error. The total error is ~2.2º peak/peak (+/-1.1º).

The sawtooth-like quantization error (see Figure 23) can be reduced by averaging, provided that the magnet is in

constant motion and there are an adequate number of samples available. The solid bold line in Figure 24 shows the

moving average of 16 samples. The INL (intrinsic non-linearity) is reduced to from ~+/- 1.1º down to ~ +/-0.3º. The

averaging however, also increases the total propagation delay, therefore it may be considered for low speeds only or

adaptive; depending on speed (see Position Error Over Speed: on page 22).

high

resolution

low

resolution

error

+1/2 LSB

-1/2 LSB

+1/2 LSB

-1/2 LSB

digitized

function

digitized

function

ideal function

Quantization

Error

INL including quantization error

-1,5

-1

-0,5

0,5

1,5

135

180

225

270

315

360

Angle steps

INL

Average (16x)

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