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

MA780 Rev. 1.2

MonolithicPower.com

22

8/30/2021

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Latency

The latency is the difference between the true

position of the mechanical angle and the angle

reading that is available on the SPI interface.

Latency is a function of the filter time constant

(τ).

Assuming the MA780 is in continuous active

mode, the latency at a constant rotation speed is

τ + 3µs. In real applications, consider the latency.

For a larger τ, the latency increases. If the

latency is high, limit the rotation speed so that

the angle error caused by latency is acceptable.

Low-Power Operation

Table 15 shows how to select the power modes.

The ASCR bit determines if the ASC mode is

controlled by the pin or the register.

Table 15: Power Modes Selection (10)

EN (Pin)

ASC

(Pin)

ASC

(Reg.)

ASCR

(Reg.)

Mode

0

0

x

0

Idle

0

1

x

0

ASC

0

x

0

1

Idle

0

x

1

1

ASC

1

x

x

x

Active

Note:

10)

“x” means not applicable.

Table 16 shows examples of typical setting for

mixed operation.

Table 16: Typical Setting for Mixed Operation

Mode

Pin for

Switching

Preset Example

ASC only

None

EN = 0,

ASCR = 1,

ASC (reg.) = 1

Active to idle

EN

ASCR = 1

ASC (reg.) = 0

Active to

ASC

EN

ASCR = 1

ASC (reg.) = 1

ASC to idle

ASC

EN = 0

ASCR = 0

Externally Switching Between Active Mode

and Idle Mode

Pulling the EN pin high activates the MA780.

After the filter settling time, the DV signal

indicates that the measurement is stable. The

master can send the MA780 back to idle mode

while the angle remains in the MA780 output

buffer, and the SPI interface remains active to

allow data reading (see Figure 32).

The SPI value is

updated

EN

DV

Start-Up

Time

Filter

Settling

Time

Idle

Active

Idle

The SPI out is the

value from the end of

the last active time

Figure 32: Signal Timing for External Control

Figure 33 shows the typical configuration to

switch between active and idle mode.

MA

EN

DV

SPI

Master

Figure 33: Typical Configuration for Switching

Between Active and Idle Mode

Mixed Operation (Active Mode and ASC

Mode)

It is possible to switch between a low-power ASC

mode and a high-power active mode by driving

the EN pin high or low, respectively. This allows

for high-rate, full power measurements after

certain angle changes are detected in ASC

mode.

Mixed Operation (ASC Mode and Idle Mode)

When switching the MA780 between ASC and

idle mode, drive the ASC state using the ASC pin

or register. ASC mode is activated when ASC is

high. In this configuration, the angle is updated

when the device is in ASC mode (see Figure 34).

MA

ASC

SPI

Master

Figure 34: Typical Configuration to Switch

between ASC and Idle Mode using the ASC Pin