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DRV8412: Driver doesn't work propely: OTW STRANGE BEHAVIOUR

raz2121
Prodigy 50 points
Part Number: DRV8412

Hi everybody.

I made custom a circuit with DRV8412 and dspic33 family Microcontroller. I use this board with 4 motors DC brushless connected with M1=M2=M3 =0;  I use 16KHz pwm.

Motors works at 12V and the signel motor can absorb max 2A.

This is what happend:

The motors are connected to a big machine of 400Kg and they have to lift it. i can reduce the weight from 100kg to 400kg.

When i lift 100kg there is no problem. driver works fine. in this case motors absorb about 700mA.

When i increase the weight to 150kg or more the OTW led indication blink quickly and after a while block the motors. ( just one driver, so 2 motors, the other 2 works fine).

I can reach max 3.3A with 4 motors( so less than 1A to motors), before it the OTW led start to blink.

Attached you can find my electrical scheme. It's just one drive. the other one is exactly the same.

I really appreciate your help. I don't know how to fix it. 

  • 0
    Prodigy 50 points
    I made typos.:

    Single Motor can absorb 2A.
    I can reach max 3.3A with 4 motors( so less than 1A to motors), before the OTW led start to blink.
  • 0 in reply to raz2121
    TI__Guru** 114905 points
    Hi raz2121,

    What is your bulk capacitor value for PVDD?
    Are you monitoring the current through the motor windings or the power supply? The power supply reports average current, but the motor current could be higher.
    What is your PWM frequency and duty cycle?

    Please note the recommendations of sections 10.1.4 and 9.4.4 of the datasheet. An example of the recommended connections of VREF, M1, M2, M3, and AGND can be found in Figure 16.
  • 0 in reply to Rick Duncan
    Prodigy 50 points

    "What is your bulk capacitor value for PVDD?"

    Sir, The capacitor on my PVDD is 100nF. are they the bulk capacitor or not? in the case could you suggest me anything about them, value and how i can connect. THe spec of my motor are wrote on the 1 post.

    Pwm frequency is 16Khz. I change the pwm duty cycle on my request to change speed and direction of motor.

    I do not have Rsense. i need to connect it or not?

    I made the modification about 10.1.4 and 9.4.4. 

    Thank you sir

  • 0 in reply to raz2121
    TI__Guru** 114905 points
    Hi raz2121,

    Typically you should have at least 220uF of capacitance on the PVDD line. The schematic example in Figure 20 shows 1000uF (C1).

    The actual capacitance value depends on a variety of factors, including:
    • The highest current required by the motor system
    • The power supply’s capacitance and ability to source current
    • The amount of parasitic inductance between the power supply and motor system
    • The acceptable voltage ripple
  • 0 in reply to Rick Duncan
    Prodigy 50 points
    Sir, thank you for your reporting. Ok i will try several value since i reach my results.

    Ok. I can see just one capacitor connected to PVDD branch(PVDD_A and PVDD_B) I have to connect another bulk capacitor on the other branch( PVDD_C and PVDD_D)?.

    Thank you again for your support
  • 0 in reply to raz2121
    TI__Guru** 114905 points
    Hi raz2121,

    I have not heard from you for awhile. Did you resolve your issue?