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DRV8704: SPI configurations for when driving two motors independently

Lenio Cacula
Genius 16260 points
Part Number: DRV8704

While the 8704 is capable of driving two motors it seems to feature a single SPI register for TORQUE, ENBL, OCPTH, and others. Is there a way to circumvent the limitation of having a single parameter for both motors, for instance, torque and overcurrent threshold?


o What are your thoughts about rail voltage or motor control when holding one motor in a stall or braking while driving the other independently?

Thank you!

  • 0
    TI__Guru 55365 points

    Lenio,

    Pablo will respond shortly.

    Regards,

    Ryan

  • 0 in reply to Ryan Kehr
    TI__Mastermind 37683 points

    Hi Lenio,

    The register parameters you listed apply for both channels. This is hard wired into the IC so cannot be circumvented. 

    Section 7.3.2 of the datasheet explains the direct PWM control which is used for driving two BDC motors. This section explains how the TORQUE and ISGAIN can be configured for non stepper control mode such as in this case. TORQUE and ISGAIN can still be used for setting current regulation limit but it will apply to both H-bridges. It is not possible to adjust parameters for each channel individually. 

    Lenio Cacula said:
    What are your thoughts about rail voltage or motor control when holding one motor in a stall or braking while driving the other independently?

    What is the purpose of keeping one motor braking/stall? I want to understand what the concern is so I can provide a more accurate response.

    Regards,

    Pablo Armet

  • 0 in reply to Pablo Armet
    TI__Genius 16260 points

    I can share more details of the application via email. For this forum, just accept that the motors need to be driven completely independently. A situation in which a motor is running while the other is braking is perfectly possible for the application. Will the regenerated energy create an issue? Are there any limitations in how the motor is controlled that would prevent this operation? I assume it's a no for both questions, but I need certainty.

    Thank you!

  • 0 in reply to Lenio Cacula
    TI__Mastermind 37683 points

    Lenio,

    Please send a meeting invite to discuss. 

    Regards,

    Pablo Armet