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

MAQ430 Rev. 1.2

MonolithicPower.com

10

8/8/2022

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© 2022 MPS. All Rights Reserved.

OPERATION

Sensor Front-End

The magnetic field is detected with integrated

Hall devices located in the center of the

package. The angle is measured using the

SpinaxisTM method, which directly digitizes the

direction of the field without complex arctangent

computation or feedback loop-based circuits

(interpolators).

The SpinaxisTM method is based on phase

detection and generates a sinusoidal signal with

a phase that represents the angle of the

magnetic field. The angle is then obtained by a

time-to-digital converter, which measures the

time

between

the

zero

crossing

of

the

sinusoidal signal and the edge of a constant

waveform (see Figure 2). The time-to-digital is

output

from

the

front-end

to

the

digital

conditioning block.

Top: Sine Waveform

Bottom: Clock of Time-to-Digital Converter

Figure 2: Phase Detection Method

The output of the front-end delivers a digital

number

proportional

to

the

angle

of

the

magnetic field at the rate of 1MHz in a

straightforward and open-loop manner.

Digital Filtering

The front-end signal is further treated to

achieve the final effective resolution. This

treatment does not add any latency in steady

conditions. The filter transfer function can be

calculated with Equation (1):

2

)

1

(

2

1

)

(

s

s

s

H











(1)

Where

τ is the filter time constant, related to the

cutoff frequency by

τ = 0.38/Fcutoff. See the

General Characteristics table on page 5 for the

value of Fcutoff.

Sensor – Magnet Mounting

The sensitive volume

of

the

MAQ430 is

confined in a region less than 100µm wide and

has multiple integrated Hall devices. This

volume

is

located

both

horizontally

and

vertically within 50µm of the center of the QFN

package. The sensor detects the angle of the

magnetic field projected in a plane parallel to

the pack

age’s upper surface. This means that

the only relevant magnetic field is the in-plane

component (X and Y components) in the middle

point of the package.

By default, when looking at the top of the

package,

the

angle

increases

when

the

magnetic field rotates clockwise. Figure 3

shows the zero angle of the unprogrammed

sensor, where the cross indicates the sensitive

point. Both the rotation direction and the zero

angle can be programmed.

Figure 3: Detection Point and Default Positive

Direction

This type of detection provides flexibility for the

design of an angular encoder. The sensor only

requires the magnetic vector to lie essentially

within the sensor plane with a field amplitude of

at least 30mT. Note that the MAQ430 can work

with fields smaller than 30mT, but the linearity

and resolution performance may deviate from

the specifications. The most straightforward

mounting method is to place the MAQ430

sensor on the rotation axis of a permanent

magnet

(i.e.:

a

diametrically

magnetized

cylinder) (see Figure 4). A typical magnet is a

Neodymium

alloy

(N35)

cylinder

with

dimensions Ø5x3mm inserted into an aluminum

shaft with an air gap between the magnet and

the sensor (surface of package) of 1.5mm. For

good linearity, the sensor is positioned with a

precision of 0.5mm.