MAQ430 – 12-BIT, AUTOMOTIVE ANGLE SENSOR WITH ABZ & UVW OUTPUTS

MAQ430 Rev. 1.2

www.MonolithicPower.com

20

8/8/2022

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© 2022 MPS. All Rights Reserved.

The X-axis or the Y-axis bias current can be

reduced to recover an equal Hall signal for all

angles and suppress the error. The parameter

ETX and ETY controls in which direction the

sensitivity is reduced. The current reduction is

set by the parameter bias current trimming

BCT(7:0), which is an integer from 0 to 255.

In side-shaft configuration (i.e.: the sensor

center is located beyond the magnet outer

diameter), k

is greater than 1. For optimum

compensation, the sensitivity of the radial axis

should

be

reduced

by

setting

the

BCT

parameter as shown in Equation (6):











 



k

BCT

1

1

258

)

0

:

7

(

(6)

Equation (6) is plotted in Figure 17 and Table 11.

0

50

100

150

200

1

1.5

2

2.5

3

3.5

4

4.5

5

k

Figure 17: Relation between the

k Ratio and the

Optimum BCT to Recover Linearity

Table 11: Example of BCT Settings

E (deg)

Magnet Ratio k

BCT(7:0)

0

1.0

0

11.5

1.5

86

19.5

2.0

129

25.4

2.5

155

30.0

3.0

172

33.7

3.5

184

36.9

4.0

194

39.5

4.5

201

41.8

5.0

207

Determining k with the MagAlpha

It is possible to deduce the k

ratio from the

error curve obtained with the default BCT

setting (BCT = 0). For this purpose, rotate the

magnet over one revolution and record the

MagAlpha output. Then plot the error curve (the

MagAlpha output minus the real mechanical

position vs. the real mechanical position) and

extract two parameters: the maximum error E

and the position of this maximum with respect

to a zero crossing am (see Figure 18). k can be

calculated with Equation (7):

)

tan(

)

tan(

m

m

a

a

E

k





(7)

-40

-20

0

20

40

0

50

100

150

200

250

300

350



m

rotor angle (deg)

2E

Figure 18: Error Curve in Side-Shaft

Configuration with BCT = 0

Some

examples

are

given

in

Table

11.

Alternatively, the k parameter can be obtained

from the graph of Figure 19.