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DRV8701: Driving DRV8701 Input IC

Nolan Lau
Prodigy 155 points
Part Number: DRV8701

Hi,

I am having issues driving the DRV8701P IC in an bi-directional mode. With the same duty cycle fed into the IC on IN1, I am seeing different speeds at the motor output shaft with no load on the motor. My setup is the following:

Forward Direction:

IN1 - PWM @ 20kHz

IN2 - GPIO High

Reverse Direction

IN1 PWM @ 20kHz

IN2 GPIO Low

I am measuring encoder index on a scope and can see a frequency output. I am concerned that I am not seeing the same frequency in both directions. Am I missing something here?

A followup question: Dan I have the following configuration to achieve the same goal?:

Forward Direction:

IN1 - GPIO High

IN2 - PWM @ 20kHz

Reverse Direction

IN1 - GPIO Low

IN2 - PWM @ 20kHz

Nolan

  • 0
    TI__Guru** 114905 points
    Hi Nolan,

    The current control is different between forward and reverse. Is the reverse path (IN1 - PWM, IN2 low) slower than the forward path?
    In the forward path, you are toggling between reverse and brake.
    In the reverse path, you are toggling between forward and coast.

    To achieve approximately the same speed, you should move the PWM from IN1 to IN2 in the reverse path, or consider using the DRV8701E. The DRV8701E allows you to PWM the EN signal while setting the direction with the PH signal.