MA780 adjust active time

Motor Drivers/Sensors
1

Hi, I’m using MA780 in the mixed operation mode (switching between “Active Mode” and “ASC Mode” using the EN pin). I read the angle every time there’s a falling edge in ND pin, and works well in ASC mode (TCYC allows adjusting the time).

When setting “Active mode”, I’m not able to adjust the active time, and it reports new information each ~210us (I want to increase it up to 1ms). I’m configuring the device with the following steps:

  • Configure TACT to 120 to get a total active time of 1ms.
  • Disable AUTACT.
  • Set the EN pin.

I’m I missing something? How can increase the acquisition period to 1ms in “active mode”?

Thank you

2

Hello apica,

Apologies for the delayed response.

When the MA780 is in Active Mode, it is performing measurements at the fastest rate and it is not affected by the TACT and AUTACT parameters, which only configure ASC Mode.

If you are still working on this application, can you please clarify why do you need the active time to be 1ms?

  • Do you just want the ND signal to toggle every 1 ms?
  • Do you want to increase the measurement resolution?

Best regards,

Carmine

3

Hello Carmine:

Picking up on this thread. I have the exact problem. I am using EN pin to make a measurement, then waiting for DV pin to toggle. Then reading data. Exactly as in figure 32 of the data sheet. Here is my usage Scenario:

  1. I want the sensor to operate in 12 bit resolution
  2. The time it takes from EN high to DV turning high is less than 200uS
  3. This time is constant irrespective of the FILTER window size (Table 14)
  4. When I repeat the reading, I am getting very stable reading
    Am i doing anything wrong? Or FW inside MA780 will convert faster if the magnetic filed is strong? If the conversion time (EN High to DV high) should vary with the FILTER WINDOW setting, then what is that I might be doing wrong?
4

Hello Pramod,

The conversion time will not change based on the magnetic field strength. Are you sure you are successfully changing the FW value? Did you try to read it?

Best,
Carmine

5

Hello Carmine:
Thank for the response. We are reading the register and making sure value in the register is correct. Can you confirm the statement below? Then we will do a more thorough debug to see what is going on.

– The time between EN going high to DV turning high will vary based on the filter window setting

Thanks
Pramod.

6

Hello Pramod,

Yes, I confirm that statement.

Best,

Carmine

7

Thank you. This issue is resolved. We root caused it to a FW bug! Now the measurement time is changing as expected with the filter window setting. Thank you for your support.

Pramod.