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I'm setting up a DRV8837 driver to work with an adjustable DC motor voltage (controlling the rotation speed). The datasheet claims

The DRV8837 is controlled using a PWM input interface, also called an IN/IN interface. Each output is controlled by a corresponding input pin.

However they supply a truth table which implies that both inputs are digital signals. How exactly could I control motor speed using PWM? Does the motor voltage needs to be the same as the logic input?

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Here's what the data sheet says: -

enter image description here

With both INs high both lower MOSFETs are on. With both INs low all MOSFETs are off.

For standard speed control IN2 should be the inverse of IN1 or vice versa and note that when mark space ratio is 50%, the motor will effectively be "held" at zero speed because it is being driven forward then in reverse is equal amounts in successive PWM timeslots.

This can be modified by holding IN1 high (for instance) and what will happen is that OUT2 will remain low and OUT1 can be PWM'd. This allows single-ended forward speed control. For single-ended reverse control hold IN2 high and OUT2 will remain low whilst OUT2 follows the PWM.

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  • \$\begingroup\$ Wouldn't hold IN2 high and PWM IN1 continuously move and brake the motor? is that healthy? \$\endgroup\$
    – joaocandre
    May 8, 2014 at 15:18
  • \$\begingroup\$ The pwm frequency is too high the worry about this on a cycle by cycle basis also, consider the first option of driving it forward and reverse.... This has to sound worse than just forward and brake! \$\endgroup\$
    – Andy aka
    May 8, 2014 at 17:09
  • \$\begingroup\$ Problem is, I would need twice the amount of PWM pins to be able to hold and pwm at will. I am considering using an inverter at one of the inputs an just PWM it. \$\endgroup\$
    – joaocandre
    May 8, 2014 at 17:19
  • \$\begingroup\$ Either way should be fine. \$\endgroup\$
    – Andy aka
    May 8, 2014 at 18:50

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