MA800 – 8-BIT, DIGITAL ANGLE SENSOR

MA800 Rev. 1.02

www.MonolithicPower.com

10

6/15/2018

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© 2018 MPS. All Rights Reserved.

Figure 4: End-of-Shaft Mounting

Figure 5 shows an example of sensor and

magnet

mounting

in a

contactless

switch

assembly.

A

Neodymium

alloy magnet

is

inserted into an aluminum shaft. The air gap

between the magnet and the sensor is 1.0mm.

The sensor is positioned on the rotation axis

with a precision of 0.5mm.

Figure 5: Example of Potentiometer-Like

Assembly

Electrical

Mounting

and

Power

Supply

Decoupling

It is recommended to place a 1µF decoupling

capacitor close to the sensor with a low

impedance path to GND (see Figure 6).

Figure 6: Connection for Supply Decoupling

In general, the MagAlpha works well with or

without the exposed pad connected to anything.

For optimum conditions (electrically, thermally,

and mechanically), it is recommended that the

exposed pad be connected to ground.

Serial Interface

The sensor supports the SPI serial interface for

angle

reading

and

register

programming.

Alternatively, the SSI bus can be used for angle

reading (programming through SSI

is not

supported).

SPI

SPI

is

a

four-wire,

synchronous,

serial

communication

interface.

The

MagAlpha

supports SPI Mode 3 and Mode 0 (see Table 1

and Table 2). The SPI Mode (0 or 3) is detected

automatically by the sensor and therefore does

not require any action from the user. The

maximum clock rate supported on SPI is

25MHz. There is no minimum clock rate. Note

that real-life data rates depend on the PCB

layout quality and signal trace length. See

Figure 7 and Table 3 for SPI timing.

All commands to the MagAlpha (whether for

writing or reading register content) must be

transferred through the SPI MOSI pin and must

be 16 bits long. See the SPI Communication

section on page 12 for details.

Table 1: SPI Specification

Mode 0

Mode 3

SCLK idle state

Low

High

Data capture

On SCLK rising edge

Data transmission

On SCLK falling edge

CS idle state

High

Data order

MSB first

Table 2: SPI Standard

Mode 0

Mode 3

CPOL

0

1

CPHA

0

1

Data order (DORD)

0 (MSB first)