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DRV10974： DRV10974 controls the motor

user5769257
Intellectual 420 points

Part Number: DRV10974

Dear team,

I used DRV10974 to control a project of motor, and encountered a problem: DRV10974 could not control the motor through PWM, and the motor was always running at high speed, unable to adjust the speed, and no FG signal was returned.

Detailed description:

When DRV10974 PWM and FG disconnect hardware signal, DRV10974 can drive motor, with FG return signal, when connected to the MCU, FG signal disappears, PWM signal can't control motor, the motor has been in high speed running state, MCU port configuration all into a state of suspension also can appear the same problem, we will try to PG signal after disconnect MCU short circuit to ground, FG signals disappear motor cannot control at the same time, if separate suspension FG signal, the PWM signal short received can speed regulation, with FG return signal.

  • 0
    TI__Mastermind 19720 points

    Hi,

    What PWM frequency are you using to drive the DRV10974? can you share the circuit of the MCU connection to the DIR, FG and PWM pins? Can you capture and share the waveforms of the FG and PWM pins? Have you tried driving the DRV10974 with a high duty cycle(90%) then back it back down to 30% and see how it reacts?

    Regards,

    Michael

  • 0 in reply to Michael.Walker
    Intellectual 420 points

    Hi,

    PWM set in any duty cycle, the motor is running at full speed, FG signal disappeared.After the power is disconnected, the M_FG, M_DIR and M_PWM are disconnected from the connection with MCU, and the FG signal is normal after the motor is started. At this time, if the pin is connected with MCU, the motor speed can be controlled.

    Best regards,

    Li

  • 0 in reply to Michael.Walker
    Intellectual 420 points

    I think we have found the reason. The problem is whether the FG signal was pulled down when it was electrified.When connecting to MCU, DRV10974 is first powered up, MCU can be powered up after a period of time delay, at this time, MCU power supply is no voltage, FG pin is equivalent to being pulled down, after pulling down FG signal, DRV10974 cannot be speed-adjusted, the speed is also the fastest, and no FG signal return.

    We have done experiments. When charging DRV10974, if FG signal is received to the ground short, DRV10974 will control the motor speed to the fastest and cannot speed at the same time.If FG signal is suspended, it can normally control the motor PWM speed regulation, FG signal is normal, please help to analyze whether there is a BUG in DRV10974, or into the factory speed regulation mode?

  • 0 in reply to Michael.Walker
    Intellectual 420 points

    The circuit is changed so that it can work properly.

  • 0 in reply to user5769257
    TI__Mastermind 19720 points

    Hi, 

    That is great that you found your systems issue. The FG pin is an open drain output so I can see why the FG pin would not be working but I do not know why having the FG pin pulled to GND would cause the motor to not spin. 

    Regards,

    Michael