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DRV8870: Motor driver recommendation inquiry

JH Shin
Guru 10950 points
Part Number: DRV8870

Hello,

My customer is testing the motor operation using the DRV8870.

When VREF 3.3V and RINSE 0.15R, they confirmed that the current of the motor was limited to 2.2A, and it continued to operate through retry.

If there is a product that stops motor operation when it is limited to 2.2A (example value), please recommend it.

Thank you.

JH

  • 0
    TI__Mastermind 37683 points

    Hi JH,

    I believe you must be confusing current regulation with overcurrent protection. The 2.2A is the current regulation limit and can be changed via the VREF or RSENSE. The OCP (overcurrent protection) limit is fixed at 3.7A (min). During current regulation, the device will continue normal operation with the switching controlled by the driver rather than the input INx signals. Now if you require the motor to stop when the current rises above 2.2A, there is method for detecting when the device is in current regulation as explained in this article. 

    Let me know if the proposed solution is possible to implement in your design.

    Regards,

    Pablo Armet

  • 0 in reply to Pablo Armet
    Guru 10950 points

    Hi Pablo,

    Thanks for your reply.

    The customer has further questions.

    1. I designed the DRV8870 with a setting of 2.2A by adjusting VREF and RSENSE.

    As shown in the graph above, it is understood as limiting the current by turning on/off the operation of the motor based on 2.2A.
    (I know that when the motor current gradually increases and reaches 2.2A (Itrip), it stops during the Toff type and operates again until it operates repeatedly up to 2.2A)

    Have I misunderstood? Is the current limit not running at 2.2A and the current limiting being executed at 3.7A?

    2. Please recommend a product that completely stops operation when 2.2A is exceeded.

    Regards,

    JH

  • +1 in reply to JH Shin
    TI__Mastermind 37683 points

    Hi JH,

    JH Shin said:
    Have I misunderstood? Is the current limit not running at 2.2A and the current limiting being executed at 3.7A?

    Your fundamental understanding is correct. The current limit is 2,2A and the OCP limit is 3.7A. During OCP fault, the entire outputs are hi-z for the duration of the auto-retry.

    JH Shin said:
    2. Please recommend a product that completely stops operation when 2.2A is exceeded.

    Unfortunately, we do not have a motor driver with OCP threshold exactly at 2.2A. However, if you have the MCU resources, you can feedback the current sensing information to an ADC of a u-controller. Once is the current is detected to be above 2.2A, the MCU stops sending the input signals to the DRV IC. This is one possible workaround. 

    Regards,

    Pablo Armet

  • 0 in reply to Pablo Armet
    TI__Mastermind 37683 points

    Hi JH,

    Does the above reply answer your question?

    -Pablp