• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 29 subscribers
  • Views 1066 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.

DRV8814: nfault issue

shuang Cao
Intellectual 385 points
Part Number: DRV8814

In the test, it is found that nFault will protect the DC motor when it starts, which causes the motor to not rotate properly, and the phenomenon repeats when it is re-energized.

Testing power supply V_MT, no abnormalities (higher than 8V) were found. Please help to analyze the reason why DRV8814 can not properly drive the motor to rotate.

Waveform (Aout1 motor current in yellow and nFLT signal in green)

  • 0
    TI__Genius 14485 points
    Hi shuang,

    Can you please retake the same scope shot above, but add a probe to measure the VMA voltage at the IC pin? Sometimes trace impedance between the power entry point on the board and the supply pin causes the power rail to dip. I know you said VM_T had no issue, but I want to double check that you are measuring in the right spot.

    If there is still no issue, the datasheet recommends putting a 1-MΩ resistor between VM and VCP. I noticed that you do not have this in your schematic. Can you add it to see if it helps?
  • 0 in reply to James Lockridge19
    Intellectual 385 points

    Hi James,

    This is the waveform after adding 1M resistance between VCM and VCP. The blue one is VCM, the green one is FAULT, and the yellow one is motor current.

    The phenomenon is the same as that without increasing the resistance, but it is better than before, that is to say, the turn will stop, now it will take a little longer to stop.

  • 0 in reply to shuang Cao
    TI__Genius 14485 points
    Hi shuang,

    Other than putting a resistor between VM and VCP, did you make any other changes to the setup? The current waveform in your second post looks much different from your first post.

    How do you have AI0, AI1, BI0, and BI1 configured?

    When you experience this condition, are you trying to drive one or two motors? Can you try driving with just one set of outputs then the other? I want to see if the issue occurs on one channel or the other.
  • 0 in reply to James Lockridge19
    TI__Genius 14485 points
    Hello shuang,

    I'm not sure if you solved your problem, so I'm going to mark this post as "TI Thinks Resolved". If you have further questions, please respond to this post or feel free to make a new one.