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DRV10983: AVS function not working

James Huntington
Prodigy 20 points
Part Number: DRV10983

I am using the Ti DRV10983PWPR to drive a 24V BLDC motor. In some cases when I need to turn off the motor, the BEMF voltage generated by the motor is returned to the power supply and the VCC voltage surges up, causing an undesirable spike. The datasheet talks about an AVS function (page 35) that is designed to prevent this but it does not appear to be working. In the SysOpt5 register, I have the Inductive AVS enabled, the Mechanical AVS enabled, the Mechanical AVS mode set to Vcc and IPD release mode set to Brake when inductive release. However, when the motor is running a high speed and the speed control register gets set to 0 to stop the motor I still see a large spike on Vcc. Do you have any suggestions? I have already gone through the tuning guide and I believe that all of my settings are correct.

  • 0
    TI__Mastermind 19720 points

    Hi James,

    I recommend that you disable the Inductive AVS and then see if that fixes your issue.

    Regards,

    Michael W.

  • 0 in reply to Michael.Walker
    Prodigy 20 points

    Thank you for the suggestion. Disabling inductive AVS appears to have resolved my issue.

    Can you explain what was happening when inductive AVS was enabled? I was looking at the revision history of the datasheet. It indicated that a previous revision had a section explaining Inductive AVS, but it was later removed. Including more detail about how AVS works in this part would be helpful (particularly when it is appropriate to use mechanical AVS and/or inductive AVS).

  • 0 in reply to James Huntington
    TI__Mastermind 19720 points

    Hi James,

    We actually removed the Inductive AVS part of the datasheet when we learned that the Inductive AVS does not work exactly as designed and will actually increase the VCC voltage surge. We now recommend to set the Inductive AVS bit to 0 and to implement a break on the system side to decrease the amount of energy that can go back into the supply. We are going to add a note to the datasheet to make this clearer. 

    Regards,

    Michael