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

MAQ430 Rev. 1.2

www.MonolithicPower.com

23

8/8/2022

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To read the MGL and MGH flags via the SPI,

send the 8-bit command write to register 27:

command

reg. address

MSB

value

LSB

0

1

0

1 1 0 1 1

0 0 0 0 0 0 0 0

The MAQ430 answers with the register 27

content in the next transmission:

Register 27 [7:0]

MGH MGL

x

x MG1LMG2L x

x

The logic state of the MGL and MGH flags has

no effect on the angle output.

MGL Application Note

Pulses with a duration of about 1.3μs to 1.5μs

appear randomly in the MGL signal. They

appear on both the 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 degrees around these

values. These pulses have an amplitude of

3.3V (VDD). The minimum interval between two

pulses is 100μs.

MGL Workarounds

1. Invert the MGH signal to replace MGL. The

MGL and MGH magnetic thresholds only

differ by a small hysteresis (see Table 14 on

page 22). 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

Front-End Diagnostics

If the thresholds are set correctly, i.e. the

magnetic field is between the MGLT and MGHT

values,

then

register

27

also

provides

diagnostic coverage of the sensor front-end.

Integrity is indicated by the following values in

register 27:

R[7:0]

0

0

0

0

1

1

1

1

ABZ Incremental Encoder Output

The MAQ430 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.