MA302 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & UVW OUTPUTS

MA302 Rev. 1.1

www.MonolithicPower.com

24

2/7/2020

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ABZ Jitter

The ABZ state is updated at a frequency of

16MHz, enabling accurate operation up to a very

high rpm (above 105 rpm).

The jitter characterizes how far a particular ABZ

edge can occur at an angular position different

from the ideal position (see Figure 25).

Figure 25: ABZ Jitter

The

measurable

jitter

is

composed

of

a

systematic jitter (always the same deviation at a

given angle) and a random jitter.

The random jitter reflects the sensor noise, so

the edge distribution is the same as the SPI

output noise. Like the sensor resolution, it is

defined as the 3σ width of this distribution.

The random jitter is a function of the rotation

speed. At lower speeds, the random jitter is

smaller than the sensor noise (see the Typical

Characteristic curves on page 7).

This is a consequence of the fact that the

probability of measuring an edge at a certain

distance from the ideal position depends on the

number of ABZ updates at this position.

The minimum field for ABZ reading is 30mT.

Block Commutation – UVW

The UVW output emulates the three Hall

switches usually used for the block commutation

of a three-phase electric motor. The three logic

signals have a duty cycle of 50% and are shifted

by 60° relative to each other (see Figure 26).

Figure 26: UVW Output for One Pole Pair Rotor

during Rotation

If the number of pole pairs of the motor exceeds

the number of pole pairs of the target magnet,

the MA302 is able to generate more than one

UVW cycle per revolution. It does this by dividing

the digital angle into the required number of

commutation steps per 360° revolution. The

parameter NPP(2:0) in register 0x7 sets the

number of

pole pairs emulated,

and the

corresponding commutation step angle for the

UVW signals. Table 18 describes the pole pair

configuration options.

Table 18: Number of UVW Pair Poles

NPP

(2:0)

Pole

Pairs

States per

Revolution

State Width

(deg)

000

1

6

60

001

2

12

30

010

3

18

20

011

4

24

15

100

5

30

12

101

6

36

10

110

7

42

8.6

111

8

48

7.5