• State
  • Locked Locked
  • Replies 6 replies
  • Subscribers 28 subscribers
  • Views 1403 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8323: Error while commanding more than 40% of the PWM

Shivaraja Narayanappa
Prodigy 120 points
Part Number: DRV8323

Hi,

I am using DRV8323H in one our project along with ATMEGA2560 for a BLDC motor Driver.

I am using the DRV8323 in 6 PWM, and proving PWM from Atmega2560 after reading the HALL SENSOR position for the motor.

The PWM frequency is set at 31KHz, and this is very well within the limit of the DRV8323. The current sens resistors of 0.001Ohm are connected on the ckt as suggested. and the gain is set to 40. IDrive is connected to GND with a 75K resistor. and VDS is connected to DVDD with 18K resistor.

I am increasing the PWM gradually from ATMEGA2560 till 40% of PWM the motor runs without any issue, after 40% of the PWM on time, the Driver is entering the Error mode. as i am using the Hardware version for this project i have no clue why this error is being occurred.

Presently the mosfet which is used is with the Gate supply of 4.5V. and the VM is 12V. Does this make any difference? I mean is the error is because of this? 

Kindly let me know if there is any why to find out what the error is?

Looking forward for your feedback.

Best Regards,

Shivaraja,N

  • 0
    TI__Expert 4435 points
    Hi Shivaraja,
    Can you describe what error mode the device enters? is the nFault pin asserted low?
    What is the status of the Charge pump at that moment?
    What is your desired current limit? Can you please monitor the output current when the driver stops working?
    If after the devices stops driving you go back to 40% PWM, does the device recovers automatically and drive?
  • 0 in reply to Luis Riveros
    Prodigy 120 points

    Hi Luis,

    Thanks for the feedback.

    Please note we are using DRV8323H where there is no SPI communication. we only have the Hardware interface. As there is no communication to the Drive, we are unable to see what error it is.

    The VDS and Idrive are connected to the DVDD, so that there is no current limit and the charge pump current is 1Amps which is maximum.

    Even after these changes the outcome is the same.

    Please feel free to revert back in case of any more clarifications.

    Looking forward for your confirmation.

    Best Regards,

    Shviaraj.N

  • 0 in reply to Shivaraja Narayanappa
    TI__Expert 4435 points
    Hi Shivaraja,

    The information requested can be observed in the DRV8323H device. You would need a scope to look closely at what those signal are doing at the moment you see the motor stop.
    - Is the nFault pin asserted low?
    - What is the Charge pump voltage at the moment motor stops?
    - Can you please monitor the output current when the driver stops working?
    - If after the devices stops driving you go back to 40% PWM, does the device recovers automatically and drive?
  • 0 in reply to Luis Riveros
    Prodigy 120 points
    Hi Luis,

    I checked it using oscilloscope, the same.
    After the 40% PWM, the error pin goes Low.
    Charge pump voltage to the Mosfets goes zero.
    When the stops, the current and voltage both goes zero.
    After this the driver will not recover automatically when the PWM goes below 40%. In order to get back the driver running the enable should go low and then High.

    I noticed the following today with Less than 40% PWM.
    - I have disabled the current Limit by connecting the VDS to DVDD( DVDD is showing 3.25VDC).
    - With the above setting the motor is not consuming the current more than 1Amps.
    - When the motor is running the motors shaft can be stopped by hand. during this motor consumes about 0.9 Amps.
    - The motor continue to run when the shaft is left free.
    - During the above process the PWM from the controller to DRV8323 is continuously provided and is not stopped.
    - But the charge pump from DRV8323 goes Zero.

    My feeling is the PWM problem will be resolved if we can remove the current limit.

    Please let me have your views and solution on the above.


    Best Regards.
    Shivaraj.N
  • 0 in reply to Shivaraja Narayanappa
    TI__Expert 4435 points
    Hello Shivaraj,
    Could you please provide a scope capture when nFault goes low. In that capture please also show VM voltage, voltage of charge pump and phase output current. Thank you.
  • 0 in reply to Luis Riveros
    Prodigy 120 points

    Hi Luis,

    Apologies for the delay.

    I have noticed the following.

    1. The VM is constant at 12V supply to the DRV8323. But the capacitors which are coupled at the Input of DRV8323 (100uf *2) are heating upto 100 Degree centigrade.

    2. I am attaching the scope images of the following.

         a.  PWM input to the INHA and GHA. ( We observed that there is voltage on GHA even when there is no PWM at INHA)

         b. PWM input to INHA and corresponding mosfet output to motor winding 1. ( The voltage at motor winding is similar to the scope at GHA).

    3. We see that the voltage at GHA is not going low even after the PWM at INHA is low.

    4. Till 40% of the PWM the motor runs without vibration. But it consumes very high current on No loaded condition( No load current reached 15Amps this is measured at the power supply input.).  Kindly let us know how do we reduce this high current.

    I have marked few areas in the Graph kindly look into it and please let us know why is that happening.

    Looking forward for your feedback.

    Best Regards,

    Shivaraj.N