MA780 – 8-BIT TO 12-BIT LOW-POWER ANGLE SENSOR

MA780 Rev. 1.2

MonolithicPower.com

9

8/30/2021

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Figure 9: Signal Timing for ASC Mode

Externally Controlled

The master

controls the MA780’s power mode

via digital input pins (EN and ASC). Switch

between any power modes using these pins.

For more details, see Table 15 and Table 16 on

page 23.

Power Supply

It is recommended to place a 1µF decoupling

capacitor close to the sensor with a low

impedance path to GND (see Figure 10).

3.3V

1µF

GND

VDD

MA780

TEST

Exposed

Pad

VDDIO

1.8V to 3.3V

Figure 10: Electrical Mounting and Power Supply

Decoupling

Generally, the MA780 works well regardless of

whether the exposed pad is connected. If both

options are possible, it is recommended not to

solder the exposed pad.

Serial Interface

The sensor supports the serial peripheral

interface (SPI) to read angles and register

configurations.

Serial Peripheral Interface (SPI)

The SPI is a four-wire, synchronous, serial

communication interface. The MA780 supports

SPI Mode 3 and Mode 0. Table 2 shows the SPI

specifications.

Table 2: SPI Specifications

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

The SPI Mode (0 or 3) is detected automatically

by the sensor, and does not require additional

action. SPI Mode 0 has a more robust data

transfer, so it is recommended to be the default

communication mode. The maximum clock rate

supported on the SPI is 25MHz. There is no

minimum clock rate. Real life data rates depend

on the PCB layout and signal trace length. For

the SPI timing, see Figure 12, Figure 13, and

Table 4 on page 12. Table 3 shows the standard

SPI values.

Table 3: SPI Standard

Mode 0

Mode 3

CPOL

0

1

CPHA

0

1

Data Order (DORD)

0 (MSB first)

All commands to the MA780 (whether for writing

or reading register content) must be transferred

through the SPI MOSI pin, and the command

must

be

16

bits

long.

See

the

SPI

Communication section on page 13 for more

details.

SPI Signal Routing on a PCB

For a reliable data transfer through the SPI bus

between the sensor (slave) and the controller

(master), special considerations should be made

for the PCB design, and the SCLK line in

particular. For the best results, follow the

guidelines below.

 Properly shield all SPI signals with a GND

plane on both sides of each trace, and shield

the GND plane underneath the SPI traces.

 Place vias along these traces to connect the

top and bottom GND planes.

 To reduce EMI issues, route the SCLK signal

away from the other SPI signals and noise

sources. The distance should be at least 3

times longer than the SCLK trace width.

SPI

out

Idle

Active

Idle

αi

αi+1