• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 29 subscribers
  • Views 429 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8308: IC controller not initiating commutation at start up when releasing the brake or setting motor speed register

user4884131
Prodigy 90 points
Part Number: DRV8308

We are experiencing some issues at BLDC motor startup. The commutation sequence doesn't seem to start the right way sometimes. We are operating the motor under BASIC mode and we change the SPEED register to change the motor speed. Sometimes, the motor doesn't start and its stalling in it's initial position and need a little push to initiate the commutation sequence in order to rotate adequately. The HALL sensors are powered by the VREG pin of the DRV8308 driver IC.

We tried to toggle the enable pin on the driver in order to power up the HALL sensors (VREG = 1) before sending the speed command, but this solution doesn't seem to work.

We also try to unconnect the hall sensors connector while the motor in stall and the motor start spinning after reconnecting the hall sensors.

Is there a specific startup sequence that we need to use in order to avoid the motor from stalling on startup?

Thanks for your help.

  • 0
    TI__Guru 61330 points
    Hello,

    It sounds like the VREG might be getting pulled down by the hall sensor inputs and have trouble when trying to come up for the first time.

    Have you tried powering the hall sensors externally after the Enable pin is set high and after waiting some time for the device to start up and VREG to charge up?

    If this is on your own board, could you send me the schematic?

    Have you tried the EVM?

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Prodigy 90 points

    Hi Adam,

    Thanks for the reply. Sorry for the delay. We Found the problem, which came from the octal switch as you are using in the EVM board to make the pseudo differential hall sensors signals from single ended Hall sensors.

    Yes, we have the EVM.

    We encountered a new problem by experiencing our drive. When we send a speed command to the motor and this one follow the accelaration curve and reach its constant speed, the lockn pin is tied high. When we set the speed register to 0, we see that the motor automaticly entered into brake mode and release the brake after about 3 seconds.

    This behavior block the motor when we tried to send a new spped command while this one is still in brake.

    Is there a way to release this brake feature for being able to send a new speed command directly after setting the speed register to 0?

    Thanks,

    Pierre-Luc

  • 0 in reply to user4884131
    TI__Guru 61330 points
    Pierre,

    I think the DRV may be looking for the hall inputs to stop switching when the speed is set to 0. Can you provide a scope image showing the three hall signals and the 3 second delay?

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    TI__Guru 61330 points
    Pierre,

    I have seen no update on this thread, did your issue get resolved?

    I will mark this thread as closed but please post if you need further assistance.

    Regards,

    -Adam