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

MA302 Rev. 1.1

www.MonolithicPower.com

22

2/7/2020

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To read the MGL and MGH flags via the SPI,

send the 16-bit read command to get the register

27 value:

command

reg. address

MSB

value

LSB

0

1

0

1 1 0 1 1

0 0 0 0 0 0 0 0

The MA302 responds with the register 27

content in the next transmission:

Register 27 [7:0]

MGH MGL

x

x MG1LMG2L x

x

Known Issue Regarding MGL

Pulses with a duration of about 1.3μs to 1.5μs

appear randomly in the MGL signal. They appear

on both pin and register values (Register 27, bit

6).

These pulses appear around angle values of 44,

138, 224, and 318 degrees (sensor output) or in

an interval of ±1.5 degree around these values.

These pulses have an amplitude of 3.3V (VDD).

The minimum interval between two pulses is

100μs.

Workarounds

1. Invert the MGH signal to replace MGL.

The MGL and MGH magnetic thresholds

only differ by a small hysteresis (see Table

16). An inverted MGH signal can be used to

replace the MGL output in the application.

2. Read the MGL signal level twice.

Using two readings, which must be between

2µs and 100µs apart, allows the user to

distinguish erroneous from real transitions.

Table 15 shows examples of different cases.

3. Read register 27 with the SPI and compute a

corrected MGL value using MG1L and

MG2L.

The corrected MGL signal = NOT (MG1L OR

MG2L). This means that the corrected MGL

must be set to 1 only when both MG1L and

MG2L

are

equal

to

0.

See

the

C

implementation below:

correctedMGL = !(MG1L | MG2L)

Table 15: MGL Multiple Reading Workaround

MGL

First

Reading

MGL Second

Reading (e.g.

20μs After the

First Reading)

True

MGL

Value

Case 1

0

Second reading is

not needed

0

Case 2

1

1

1

Case 3

1

0

0

ABZ Incremental Encoder Output

The MA302 ABZ output emulates a 10-bit

incremental

encoder

(such

as

an

optical

encoder) providing logic pulses in quadrature

(see Figure 22). Compared to signal A, signal B

is shifted by a quarter of the pulse period. Over

one revolution, signal A pulses N times, where N

is programmable from 1 to 256 pulses per

revolution. The number of pulses per channel

per revolution is programmed by setting the

parameter PPT, which consists of eight bits split

between registers 0x4 and 0x5 (see Table 5).

The factory default value is 256. Table 16

describes how to program PPT(7:0) to set the

required resolution.

Table 16: PPT

PPT(7:0)

Pulses per

Turn

Edges per

Turn

00000000

1

4

MIN

00000001

2

8

00000010

3

12

00000011

4

16

…

…

…

…

11111100

253

1012

11111101

254

1016

11111110

255

1020

11111111

256

1024

MAX

For example, to set 120 pulses per revolution

(480 edges), set PPT to 120 - 1 = 119 (binary:

01110111). Registers 4 and 5 must be set as

shown in Table 17.

Table 17: Register 4 and Register 5

B7

B6

B5

B4

B3

B2

B1

B0

R4

1

1

0

0

0

0

0

0

R5

0

0

0

1

1

1

0

1