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

MA780 Rev. 1.2

MonolithicPower.com

21

8/30/2021

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Table 13: Trimming Direction Parameters

ETX

Enable Trimming of the X-Axis

0

Disabled

1

Enabled

ETY

Enable Trimming of the Y-Axis

0

Disabled

1

Enabled

Status Byte

Register 26 contains information about the

sensor

’s operational integrity.

ERRPAR

When using 17-bit communication on the SPI

bus, the SPI write register command sent by the

controller to the sensor can be checked for parity

(unlike the other commands). The controller

sends a parity bit on the MOSI line after the 16-

bit command. The sensor checks the parity of

the 17-bit long command. If there is a parity error,

then the data to be written to the register is

discarded and the ERRPAR bit asserts (set to 1).

ERRMEM

The ERRMEM bit asserts (set to 1) if an SPI write

register command is sent while the NVM is busy

(NVM pin is high). To avoid raising the ERRMEM

flag, the user must ensure that no SPI write is

sent while the NVM pin is high (set to 1). It is also

recommended to check that the register value

returned by the SPI write register command

matches the desired written value (see the SPI

Write Register section on page 14).

ERRNVM

Restoring register values from the NVM is

secured by a cyclic redundancy check (CRC)

algorithm. If the generated CRC result does not

match the stored value (called a mismatch), the

ERRNVM bit asserts (set to 1). If any error flag

is asserted, the ERR pin is set to logic 1. Clear

the error flags and ERR pin by sending the SPI

Clear Error Flags command.

Filter Window Size

The filter window (FW) determines the effective

resolution (defined as the ±3

σ noise interval).

Figure 31 shows the effective resolution for

different FWs and the magnetic field (B).

Figure 31: MA780 Resolution

Since FW modifies the filter time

constant (τ),

FW impacts the output bandwidth. The upper

limit of the bandwidth and the cutoff frequency

(fCUTOFF) are related to τ. fCUTOFF can be estimated

with Equation (6):

fCUTOFF = 0.16/ τ

(6)

When the MA780 enters active mode (whether it

is externally controlled or in ASC mode), the

digital filter has to settle . Therefore, the angle

output is not stable until a certain amount of time

has passed (called the filter settling time). This

time is indicated by the data valid flag (DV output

pin). Table 14 show the time constant and the

settling time for each window size.

Table 14: Filter Window Size (9)

Filter

Window

FW[3:0]

τ (µs)

Filter Settling

Time (µs)

fCUTOFF

(Hz)

0

1

1

160,000

1

2

3

79,600

2

4

7

39,800

3

8

15

19,890

4

16

31

9,950

5

32

63

4,970

6

64

127

2,490

7

128

255

1,240

8

256

511

622

9

512

1023

311

10

1024

2047

155

11

2048

4095

78

12

4096

8191

39

13

4096

8191

39

14

4096

8191

39

15

4096

8191

39

Note:

9) See the Electrical Characteristics section on page 4 for the filter

settling time accuracy.