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

MA302 Rev. 1.1

www.MonolithicPower.com

13

2/7/2020

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SPI Communication

The sensor

supports three types

of

SPI

operation:

 Read angle

 Read configuration register

 Write configuration register

Each operation has a specific frame structure

described below.

SPI Read Angle

Every 1µs, new data is transferred into the output

buffer. The master device triggers the reading by

pulling CS low.

When a trigger event is detected, the data

remains in the output buffer until the CS signal is

de-asserted (see Table 4).

Table 4: Sensor Data Timing

Event

Action

CS falling edge

Start reading and freeze

output buffer

CS rising edge

Release of the output buffer

See Figure 9 for a diagram of a full SPI angle

reading. See Figure 10 for a diagram of a partial

SPI angle reading. A full angle reading requires

16 clock pulses. The sensor MISO line returns:

MSB

LSB

MISO

Angle(15:0)

MOSI

0

The MagAlpha family has sensors with different

features and levels of resolution. Check the data

output length in the General Characteristics table

on page 5 for the number of useful bits delivered

at the serial output. If the data length is smaller

than 16, the rest of bits sent are zeros.

For example, a data output length of 12 bits

means that the serial output delivers a 12-bit

angle value with four bits of zeros padded at the

end (MISO state remains zero). If the master

sends 16 clock counts, the MagApha replies

with:

MSB

LSB

MISO

Angle(15:4)

0 0 0 0

MOSI

0

Angle reading can be therefore optimized

without any loss of information by reducing the

number of clock counts. In the case of a 12-bit

data output length, only 12 clock counts are

required to get the full sensor resolution.

MSB

LSB

MISO

Angle(15:4)

MOSI

0

If less resolution is needed, the angle can be

read by sending even fewer clock counts (since

MSB is first).

In case of fast reading, the MagAlpha keeps

sending the same data until the data is refreshed

(see

the

refresh

rate

in

the

General

Characteristics table).

Figure 9: Diagram of a Full 16-Bit SPI Angle

Reading

Figure 10: Diagram of a Partial 8-Bit SPI Angle

Reading

SPI Read Register

A read register operation is constituted of two 16-

bit frames. The first frame sends a read request

which contains the 3-bit read command (010)

followed by the 5-bit register address. The last

eight bits of the frame must be all set to zero. The

second frame returns the 8-bit register value

(MSB byte).