• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 29 subscribers
  • Views 528 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TI DRV8821/DRV8823

vineet kumar
Intellectual 730 points
Other Parts Discussed in Thread: DRV8823, DRV8821

Hi

I am presently using TI DRV8821/DRV8823 motor driving module. the problem i am facing is unpredictability of the output at the motor output pin . I am using the DRV8823 MODULE application software where i am making the following settings

AENABLE   MARK

APHASE    MARK

ADECAY   MARK

RESET      MARK

SLEEPN   MARK

when i am changing the reference voltage i.e VREFAB to 0 i sometime i got 12 volt and sometime 24 volt on the A+ AND A- PIN OF THE BOARD.

please help me out in configuring the board .

  • 0
    Prodigy 135 points

    Hi Vineet,

    How are you measuring the voltage at the output? A multimeter? A Scope?

    Remember the DRV8821/23 is a current chopper topology power stage which means outputs will be switching in order to regulate current againt the programmed command as specified by the SENSE resistor and the VREF analog input while following the ITRIP equation specified in the datasheet.

    If you try to measure voltage with a meter, I would not even try to make sense of this reading.

    If you are seeing the 12V (even when VM is 24V) with a scope, what are the outputs connected to? If they are connected to a motor, I would expect to see the outputs swing from 0V to 24V. But if they are connected to resistors, then you can see 12V when the outputs are floating. Outputs can get to a floating state either when you disable the H Bridge or when the H Bridge enters fast decay and current reaches zero (outputs are tri-stated until new current chop cycle).

  • 0 in reply to Avayan
    Intellectual 730 points

    Hi Avayan

    I am measuring the voltage using multimeter. The problem i am facing is all the motor that i have is of 12V rating , so inorder to check the voltage comming on the respective output i used multimeter to verify the voltage. I am new in this field and i have gone through the data sheet as well but i am not able to tap THE CHOPPER TOPOLOGY that you are referring .

    I have shorted circuited one of the DC MOTOR that i have interfaced with the motor driver board.

    i would be really greatful if you tell me about the CHOPPER TOPOLOGY or any link that is related to it so that i can understand the DRV8821/DRV8823 good and make use of the 12V rated motors.

  • 0 in reply to vineet kumar
    TI__Guru 55655 points

    Vineet,

    The chopper topology that Avayan is referring too is explained under page 8 of the DRV8821 datasheet.  It uses a basic comparator circuit to monitor the voltage across an external sense resistor.  When the comparator trips, the bridge is disabled and current is recirculated through one of the decay modes...also described in the datasheet.