A31316 datasheet(23/61 Pages) ALLEGRO

23 / 61 page

3D Magnetic Position Sensor IC

A31316

Allegro MicroSystems

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

VARIABLE SEGMENT LINEARIZATION (LIN_MODE 2)

x_pos_00

x_pos_01

Y_val_01 ( value < 0 )

Y_val_00 ( value < 0 )

Figure 14: Variable Segment Linearization

In variable-segment linearization mode, between 2 and 22 output

correction points are positioned at user-selected positions. The

correction codes Y_val_xx are in signed 13-bit format and repre-

sent a correction using the format in the table below:

Table 7: Y_val_xx range depending on lin_coeff_scalar setting

lin_coeff_

scalar

Range (°)

Value for code

–4096 (°)

Value for code

+4095 (°)

Step size (°)

±45

+45

–44.99

90/213 ≈ 0.011

±90

+90

–89.98

180/213 ≈ 0.022

±180

+180

–179.96

360/213 ≈ 0.044

±360

+360

–359.91

720/213 ≈ 0.088

Most applications will have monotonically rising outputs. How-

ever, the sensor can support rising and falling outputs if needed.

The position codes X_pos_xx are in unsigned 6-bit format and

represent positions of 0° (X_pos_xx = 0) to 354.375° (X_pos_xx

= 63). The X values must be placed in a rising manner, so that the

value of X_pos(n+1) ≥ X_pos(n).

If the result of the linearization is outside the 0–360° range, the

value will be clipped to 0° or 360°. No overflow will happen in

the linearization block. This means that for rotary applications,

the 0° correction value and the 360° correction value must both

be set to 0.

For input values below the angle defined by the X_pos_00 value,

the linearization function will extrapolate the slope set by the first

two defined points. For input angles above the angle defined by

the last X_pos_xx value, the linearization function will extrapo-

late the slope set by the last two defined points. For input angles

between 354.375° and 360°, this will always happen, and there is

no other way to control the behavior in this area than by making

use of the extrapolation of the two previous points. The extrapo-

lating behavior is shown in Figure 13 for both low and high input

values

VARIABLE SEGMENT BINNING (LIN_MODE 3)

x_pos_00

x_pos_08

Y_val_00

Y_val_08

Figure 15: Variable Segment Binning

In variable-segment binning mode, between 2 and 21 bins are

equidistantly positioned between 0° and 360° input. The binning

output codes Y_val_xx are in unsigned 13-bit format and repre-

sent an output value of 0° (Y_val_xx = 0) and 359.96° (Y_val_xx

= 8191). Any value is mapped to the bin as an input angle below

that of the input, i.e. the bin that the output ends up in is the bin

whose X value is “to the left” of the measured angle. The param-

eter lin_coeff_scalar has no meaning in binning mode.

The position codes X_pos_xx are in unsigned 6-bit format and

represent positions between 0° (X_pos_xx = 0) and 354.375°

(X_pos_xx = 63). The X values must be placed in a rising manner,

so that the value of X_pos_(n+1) ≥ X_pos_(n).

If X_pos_00 does not define a bin at position 0°, a bin with X_pos

= 0°, Y_val = 0° will be automatically assumed.

LINEARIZATION/BINNING PARAMETER STORAGE

The individual linearization/binning parameters are stored in the

EEPROM parameters lin_coeff_00 … lin_coeff_32. Depend-

ing on the linearization/binning configuration, the contents of

these memory locations have different meanings. All modes and

EEPROM field contents are listed in Table 12. Parameters that

are not used for linearization may be used otherwise. The param-

eters lin_coeff_17 … lin_coeff_31 can be sent out through the

SENT enhanced serial message for certain constants (see Table

20). If they are used in this manner, the parameter coeff_active

must be set in such a way that these two usages do not interfere

(see Table 13).

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