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Stepper motor controllers/drivers in parallel

Hugo Goncalves
Prodigy 10 points
Other Parts Discussed in Thread: DRV8811, DRV8800, DRV8828, DRV8829, DRV8825

Hi there,

Can controllers/drivers such as the DRV8811 work in parallel to supply more current to the motor?

I can see that deviations in Rds(on) can lead to current flowing more through one driver than the other or lead to chopping in different times, but what are the implications of that?

Thanks,

Hugo Gonçalves

  • 0
    TI__Intellectual 1100 points

    Hugo -

    In some cases, drivers may be connected in parallel.  For example, the DRV8800 is characterised to be used that way.  Unfortunately, with most of the drivers like the DRV8811, it is not recommended.

    The problem is that there can be small timing differences between devices.  They would have to be exactly synchronized in order to be connected in parallel, otherwise there could be a situation where one device is driving the ouput low while the other is driving it high, which would cause a shoot-through condition between power and ground.  This gets even more complicated when current control is being used, as slight differences in the current chopping threshold from one part to the other would cause the parts to try and change the PWM cycle at different times.

     

  • 0 in reply to Pete Millett
    Prodigy 70 points

    DRV8811 has peak drive current 2.5A.

    I also mind to use DRV8811 because my stepper motors runs at 3.0A.

    So I am testing DRV8811 EVM now to drive 3.0A stepper motor.

  • 0 in reply to Paul Jay
    TI__Expert 7455 points

    Hi Paul,

    Not certain how much current you actually need, but to reach the 2.5A on the DRV8811 will be tough. If you do require to get closer to the 3A mark, allow me to recommend to use two DRV8828 devices. The system will be a little bit more complex, but it will definitely be able to drive the 3A motor better.

    Now, the DRV8828 is rated at 3A, so at this current you are also reaching a peak. However, the advantage of developing a system with the DRV8828 is that as soon as the DRV8829 is released in a few months, you will be able to drop it in (identical in layout) and then you will have about 5A worth of current per winding.

    If you need less than 2A, then the DRV8811 or even the DRV8825 are the way to go. DRV8825 will not be released for a few more months, though, but it has lower RDS ON and higher degrees of microstepping (32), in case you need this feature.

    Best regards,

    JIQ

  • 0 in reply to Jose Quinones
    Prodigy 70 points

    Thank you for your comment.

    I am using 2A rated Bipolar steppers and one 3A rated Bipolar stepper. So I need peak 3A driver circuit.

    Today I have tested actually the steppers with DRV8811 EVM on my machine. For high load, more current in the winding was needed.

    And DRV8811 was getting hot quickly when running 3A rated bipolar stepper. Microstepping was perfect adjusting decay and current.

    I would like to test DRV8828. Is the DRV8828EVM available at estore.ti.com ?

    Best Regards,

    Paul

  • 0 in reply to Paul Jay
    TI__Expert 7455 points

    Hi Paul,

    If you contact me at my personal email address (jquinones@ti.com), we can arrange to send you a demo board with the DRV8829 device. It is the high resolution application note board.

    This is the same board I used on my personal CNC project and it worked gorgeously! This is the route I recommend for CNC equipment. There was another gentleman in California who adopted it as well, and was using the 32 degrees of microstepping feature embedded into the Ix current control bits. I personally use the VREF technique. You can use either.

    Since you only want 8 degrees of microstepping I would go with the Ix technique. You could implement it in a superbly economical microcontroller.

    There is also an application note on how to do this and I can send you the code. You can find it here:

    http://focus.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=slva443&fileType=pdf

    Currently I am working on the DRV8828/29 EVM as the first one we designed was intended as a single device EVM which is a moot point as you  need two devices anyway to drive a stepper. The EVM that I am designing will incorporate both application notes (high resolution through VREF and mod resolution through Ix bits). It will be about two months before it can be purchased through the TI store, so my apologies for that gross delay.

    I can get you up and running with an App Note Demo Board in the mean time, though.

    Best regards,

    JIQ

  • 0 in reply to Jose Quinones
    Prodigy 70 points

    dear Jose,

    I have sent you an E-mail. I will study DRV8828/8829 datasheet and application note.

    Thank you.

    Paul J