• State TI Thinks Resolved
  • Locked Locked
  • Replies 14 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 1145 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.

DRV8876: spark between CPH and CPL pin

sharon thomas
Prodigy 70 points
Part Number: DRV8876

i am using drv8876 to control dc motor. supply voltage given is 24v. i am using six such motor drivers on my board. it worked properly for sometime. After that there was continuous spark and smoke around CPH pin. can anyone tell what might be the reason?

  • 0
    TI__Mastermind 37683 points

    Hi Sharon,

    Was this issue been observed in more than one motor driver? Can you share schematic near the driver?

    A possible explanation could be an unexpected short either from CPH-to-GND, CPH-to-VM, or CPH-CPL. I recommend doing a continuity test between these three possible shorting scenarios to determine if there is a short. Make sure there is no power going to the driver when performing the short tests.

  • 0 in reply to Pablo Armet
    Prodigy 70 points

    yeah, issue has been observed with more than one driver. i have performed the short tests. there was no short between any of the above mentioned pins. so i replaced the ic with another one. still same issue has been observed. when we power on the board there is a continuous spark and fumes between CPH and CPL pins.

    Recommended capacitor between CPH and CPL is X5R or X7R. i am using Y5V cap. will that be an issue?

  • 0 in reply to sharon thomas
    TI__Mastermind 37683 points

    Hi Sharon,

    Yes. we recommended X5R or X7R capacitors because they have lower change of capacitance over temperature.

    Can you replace the Y5V capacitors with either X5R or X7R?

  • 0 in reply to Pablo Armet
    Prodigy 70 points

    I checked all the pins of DRV8876 IC using a MDO. spark and fumes observed around CPH and CPL pin. it is also observed that fault pin is high. and the ic is still working with and without load. current drawn was around 100mA without load. Images of the Signals at CPL and CPH pins are attached with this.

    tied sleep pin to ground . no spark or fumes observed. current drawn was 40mA.

  • 0 in reply to sharon thomas
    Prodigy 70 points

    i will replace the Y5V capacitors with either X5R or X7R and will get back to you.

    thankyou

  • 0 in reply to sharon thomas
    TI__Mastermind 37683 points

    Hi Sharon,

    Thank you for sharing the waveforms. Please let me know when you replace the capacitor and test it.

  • 0 in reply to Pablo Armet
    Prodigy 70 points

    i replaced the capacitor with X7R . issue still exists. drv8876 IC temperature is high.draws around 100mA without load.

    how do you choose value of  the capacitor between CPL and CPH?

    why there is 24v present on the CPL pin(check waveform)? when i checked other working IC's it was not the case.

  • 0 in reply to sharon thomas
    TI__Guru 55615 points

    Sharon,

    Recommended capacitor values are given in Table 1 of the datasheet.  

    Can you please share your schematic and layout?  

    Do you have an EVM you can test and see what the waveforms should look like as a reference.  

    CPL pin should be near ground potential.  It makes me wonder if the part is properly connected to GND on your board.  

  • 0 in reply to Ryan Kehr
    TI__Mastermind 37683 points

    Hi Sharon,

    Any updates? Were you able to figure out the root cause of the issue?

  • 0 in reply to Pablo Armet
    Prodigy 70 points

    i was not able to figure the root cause. driver ic is working but it heated up abnormally. couldn't find the actual reason.

  • 0 in reply to sharon thomas
    TI__Mastermind 37683 points

    Hi Sharon,

    Thank you for the update.

    sharon thomas said:
    why there is 24v present on the CPL pin(check waveform)? when i checked other working IC's it was not the case.

    I realized i missed this question from a previous reply. What was the CPL voltage for the working IC? can you provide a waveform showing CPL, CPH, and VCP for both the failed and working ICs? It looks like there something happening with the charge pump on the failed ICs.

  • 0 in reply to Pablo Armet
    TI__Mastermind 37683 points

    Hi Sharon,

    Were you able to take the waveforms? What's the status of your issue?

    Feel free to reply back to this post if you require further assistance.

  • 0 in reply to Pablo Armet
    Prodigy 70 points

    CPH pin of working ic

    first image shows the waveform on CPH pin of working drv8876 IC

    cpl pin of working ic

    second image shows the waveform on CPL pin of working drv8876 IC

    CPH of fault ic

    third image shows the waveform on CPH pin of faulty drv8876 IC

    cpl pin of faulty ic

    fourth image shows the waveform on CPL pin of faulty drv8876 IC

    vcp pin of faulty ic

    fifth image shows the waveform on VCP pin of faulty drv8876 IC

  • 0 in reply to sharon thomas
    TI__Mastermind 37683 points

    Hi Sharon,

    Thank you for providing the information.

    The VCP of the faulty device is lower than the expected typical value. So the charge pump is definitely not operating properly.  I can't really think of an explanation for it at the moment. Please give me one business day to research.

    Do you think you can share your driver schematic? I want to take a look at the charge pump components. You can share it via private message if you don't want to share in the forum.

    How are you providing power to the driver? are you using a switch or is it directly connected to a bench power supply? I have observed some issues occurring in the charge pump (leakage current and high temperatures) when very large VM slew rates are applied to the device. Normally, bulk capacitors near the power entry point of the board will help minimize the VM slew rate. Our devices have a maximum slew rate for safe operation.