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DRV8701: The driver output torque is too small

Cherry Zhou
Mastermind 22235 points
Part Number: DRV8701

Hi team,

Here's an issue from the customer may need your help:

The motor drives are powered from the power supply, the motor turns fast when no load, the forward and reverse speed is regulated, the torque is also large, and other functions are normal. But when running on a 7.4-V nickel-chromium battery, it also works well if the motor is not loaded, and if a sudden heavy load is applied, for example, by holding the wheel with your hand during normal rotation, the motor does not output torque (no torque at all) and also makes noise (humming). And the schematic is as follows:

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Mastermind 37683 points

    Hi Cherry,

    The schematic looks good to me. I do have some questions however:

    1. Is the power supply voltage same as battery voltage (7.4V)?
    2. has the customer monitor the voltage at VM during the period of heavy load?

    If the motor is not spinning when load is applied, it most likely means the current is not sufficient to provide the required torque needed to keep the motor spinning. Increasing the supply voltage is one way of fixing it.

    Regards,

    Pablo Armet

  • 0 in reply to Pablo Armet
    TI__Mastermind 22235 points

    Hi Pablo Armet,

    Thanks for your support!

    Pablo Armet said:
    If the motor is not spinning when load is applied, it most likely means the current is not sufficient to provide the required torque needed to keep the motor spinning.

    Yes, the customer has found that's the case here.

    Also here's a new condition, the chip VM is 7.4 V with a multimeter, but the current is small. After replacing all the power lines, the motor torque is very high, but after a while the motor is not working again, why is that? Is it due to poor wire contact?

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Mastermind 37683 points

    Hi Cherry,

    Cherry Zhou said:
    Also here's a new condition, the chip VM is 7.4 V with a multimeter, but the current is small. After replacing all the power lines, the motor torque is very high, but after a while the motor is not working again, why is that? Is it due to poor wire contact?

    Could be the case. Can they provide images of their connector with the power cables.

  • 0 in reply to Pablo Armet
    TI__Mastermind 37683 points

    Hi Cherry,

    Any updates from the customer? Has the issue been resolved?

    I will close this thread if no help is needed but you can reply if further support is required.

    Regards,

    Pablo Armet