• State
  • Locked Locked
  • Replies 6 replies
  • Subscribers 29 subscribers
  • Views 453 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.

DRV8821, all outputs reading ground + heating of chip

Stephen Wolf
Prodigy 30 points
Other Parts Discussed in Thread: DRV8821

So I have a DRV8821 dual stepper motor controller that I have soldered on my board and powered by 12V. I have checked all the pins and verified no shorts between any ground/power pins, digital inputs, or anything like that.

 

So when I apply the digital inputs of Reset off (high), Motor off (high) and some of my direction/decay modes nothing happens as expected. The chip stays cool, all outputs measure ground.

 

However when I turn motor enable low I expect to get an output on at least one of the coils. Without a motor attached I don't expect any heating. However the opposite occurs, all my outputs stay at ground and my controller starts to get hot. Applying a low frequency (~60Hz)  square wave to the STEP input does nothing.

 

What can cause this? I really hope I didn't destroy the chip while soldering it in place but I can't think of anything else that would cause those symptoms of total non-functionality.

  • 0
    Prodigy 30 points

    I have been able to fix the problem and make the motor spin. My capacitor attached to V3P3 (the 3.3V regulator output) was shorted to ground and I forgot to test it since it was on the other side of the board. I am unsure why it would make the motor controller act like it did but it works correctly once I replaced it with another bypass capacitor.

  • 0 in reply to Stephen Wolf
    TI__Expert 7455 points

    Hi Stephen,

    I am thinking the observed behavior makes sense as in essence the internal 3.3V rail was getting shorted to GND. This would of course imply a total collapse of the logic power supply (the device can not operate withouth the logic blocks) and a low ohmage path to ground causing the heating.

    Glad to see you were able to solve the problem!

    Best regards,

    Jose Quinones

  • 0
    Prodigy 40 points

    Hi,

    I want to design my own custom  pcb layout for stepper motor driver using DRV 8821, and control that using ez430-RF2500 devlopment pins available on that board . also I wanted to know how to design or is it possible to design a single layer pcb layout or anyother alternative for prototyping?

  • 0 in reply to mahendra khened
    TI__Expert 7455 points

    Hi Mahendra,

    A design around the DRV8821 will most likely benefit from a layout with at least 2 layers. Ideally you would want to use four layers for better thermal impedance but we understand the cost of such board may be prohibitive for certain cost sensitive applications.

    For guidelines on how to design your own PCB we recommend you take a look at the SLMA002 application note. Also, I am attaching the EVM Gerber Files where you can see how we implemented this design. Although it is a four layer board, only two layers carry the actual control and power signals. You can of course disregard all the test stakes which are only present on the EVM for evaluation purposes, a feature the actual application will most likely not require.

    7065.CPG003_Gerbers.zip

    Hope the info helps. Best regards,

    Jose Quinones