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

MA780 Rev. 1.2

MonolithicPower.com

23

8/30/2021

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Configurations for ASC Mode

The power cycles are defined by the active time

and the cycle time. By default (AUTACT = 1), the

active time is automatically adjusted to the filter

window, such that the active time ends when the

filter has settled. The active time (tACTIVE) can be

calculated with Equation (7):

ACTIVE

START UP

SETTLING

t

t

t





(7)

Where tSETTLING can be determined by Table 14

on page 22. ASC mode is recommended for

most applications. Figure 35 shows the timing for

an ASC cycle.

ND

(THR = 0)

SPI Out

Idle

Idle

Start-Up

Time

Filter

Settling

Time

Data Valid =

Output Updated

Angle SPI Reading

tACTIVE

Active

Figure 35: Timing of a ASC Cycle when THR = 0

and AUTACT = 1

If AUTACT is disabled, the active time is defined

by the TACT parameter. The active time ranges

between 40µs and 2056µs, with 8µs per step

(see Table 17).

Table 17: Active Time

TACT[7:0]

tACTIVE (µs)

0

Do not use

1

Do not use

2

Do not use

3

40

4

48

5

56

…

…

255

2056

If TACT[7:0] exceeds 2, tACTIVE (in µs) can be

calculated with Equation (8):

ACTIVE

t

( s)

8 TACT[7 : 0] 16

  



(8)

Table 17 lists potential times for tACTIVE (see the

Electrical Characteristics on page 4 for active

time accuracy).

The active time should be set such that the angle

output is stable (the filter has settled and the data

is valid). This means the active time should

exceed the valid data time. tACTIVE can be

estimated with Equation (9):

ACTIVE

START UP

SETTLING

t

t

t





(9)

Figure 36 shows the timing of an ASC cycle.

ND

(THR = 0)

SPI Out

Idle

Idle

Output

Updated

Start-Up

Time

Filter

Settling

Time

Data

Valid

Angle SPI

Reading

tACTIVE

Active

Figure 36: Timing of an ASC Cycle when THR = 0

AUTACT = 0

Cycle Time

The ASC cycle time is set by the TCYC

parameter. TCYC can be directly configured by

the user. The cycle time must be longer than the

active time (see Table 18). Otherwise, the cycle

time increases by an integer number of times

until it is longer than tACTIVE .

Table 18: Cycle Time

TCYC

Cycle Time (ms)

0

Continuously idle

1

Do not use

2

0.2

3

0.3

4

0.4

…

…

65535

6553.5

See the Electrical Characteristics section on

page 4 for the cycle time accuracy.

Once the TACT and TCYC parameters are set,

the

average

current

consumption

can

be

calculated with Equation (10):