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DRV8889-Q1: Does the voltage across the coils regulate down below the Vm min of 4.5V?

Jonathan Geronga
Expert 7930 points
Part Number: DRV8889-Q1

Hi Team,

I have a couple of questions from the customer regarding DRV8889-Q1 below:

The customer is looking at using a motor with Rcoil=5.6 ohm, and current rating of .67A. This leaves rated voltage of 3.8 volts. He will have a Vm of around 22V (adjustable if lower voltage is desired).
Here are the questions:
One is, "Will the DRV8889 (assuming Vref and TRQ_DAQ set appropriately) be able to regulate to 0.67 A, where the voltage across the coils are 3.8V (steady state)?". If the answer to the first question is yes, then how low can the current be adjusted in a steady state. i.e. to hold the motor in a fixed location, can the driver still regulate the current down to say .3A which would be a voltage of 1.68 V across the coils? How low can the driver work in steady state in terms of voltage across the coils?

Thanks,

Jonathan

  • 0
    TI__Genius 13455 points

    Hi Jonathan,

    Yes, this is not a problem.  The driver itself regulates current, and the measured voltage across the coil will be based on its resistance and the desired current setting.

    The regulated current can be changed a few ways.  If the controller has a PWM or DAC output, it may be desirable to have VREF driven by the controller.  There is also the TRQ_DAC register that allows you to keep VREF at a steady voltage, and adjust current by programming the register and saves an MCU pin/ DAC/ PWM resource.

    Regards,
    Mike