MA800 – 8-BIT, DIGITAL ANGLE SENSOR

MA800 Rev. 1.02

www.MonolithicPower.com

18

6/15/2018

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REGISTER SETTINGS

Zero Setting

The zero position of the MagAlpha (a0) can be

programmed with 16 bits of resolution. The

angle streamed out by the MagAlpha (aout) is

given by Equation (2):

0

a

a

a

raw

out





(2)

Where araw is the raw angle provided by the

MagAlpha front-end.

The parameter Z(15:0), which is zero by default,

is the complementary angle of the zero setting.

It can be written in decimals using Equation (3):

)

0

:

15

(

2

16

0

Z

a





(3)

Table 10 shows the zero setting parameter.

Table 10: Zero Setting Parameter

Z(15:0)

Zero pos.

a0 16-bit (dec)

Zero pos.

a0 (deg)

0

65536

360.000

1

65535

359.995

2

65534

359.989

…

…

…

65534

2

0.011

65535

1

0.005

Example

To set the zero position to 20 deg, the Z(15:0)

parameter must be equal to the complementary

angle shown in Equation (4):

61895

2

deg

360

deg

20

2

)

0

:

15

(

16

16







Z

(4)

In binary, this is written as 1111 0001 1100

0111.

Table 11 shows the content of registers 0 and 1.

Table 11: Register Content

Reg Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

0

1

1

0

0

0

1

1

1

1

1

1

1

1

0

0

0

1

Rotation Direction

By default, when looking at the top of the

package,

the

angle

increases

when

the

magnetic field rotates clockwise (CW) (see

Figure 18 and Table 12).

Figure 18: Positive Rotation Direction of the

Magnetic Field

Table 12: Rotation Direction Parameter

RD

Positive Direction

0

Clockwise (CW)

1

Counterclockwise (CCW)

Magnetic Field Thresholds

Push Button Detection

The MA800 has two threshold options (MGHT

or

MGLT),

which

are

complementary

in

operation. The flag MGH becomes TRUE (logic

1) if the magnetic field increases above MGHT.

The flag MGL becomes TRUE (logic 1) if the

magnetic field falls below MGLT (see Figure 19).

Figure 19: MGH and MGL Signals as a Function

of the Field Strength

The MGL and MGH flags can be used for

detecting an approaching magnet (e.g.: when a

button is pressed). With the 5mmx3mm magnet

example, if the MGHT threshold is set to binary

110 (106 - 112mT), the MGH signal is set to

logic high when the sensor-magnet airgap is

smaller than 1.0mm (see Figure 20).