• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 630 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.

DRV8251: Passive components for outputs

Yosuke Tezuka
Prodigy 10 points
Part Number: DRV8251

Dear Design support team, 

Now I'm testing the chip [DRV8251]. I wanted to know if there are any passive components (with resistor value and capacitor value) for output lines as you recommended. It would be really appreciated if you give me the information.

Best regards,

  • 0
    TI__Guru 55615 points

    Hello!

    What exactly are you trying to achieve with these passive components?  That would help us with recommendations.

    Regards,

    Ryan

  • 0 in reply to Ryan Kehr
    Prodigy 10 points

    Thank you for your reply! Outputs directly go to a BDC. The BDC drives a load. Current regulation is not used in my design so ISEN is directly connected to the ground.

    When the outputs were directly connected to the BDC and put input signal, the BDC stopped at the moment. Sometimes the BDC run, and released input signal, and then the BDC got free (stopped working). That phenomenon seemed that OCP worked because of inrush/backrush current.

    Then I tried to measure the voltage with using a oscilloscope. Probes were plugged to OUT1 and OUT2. And then, the motor worked very well, CW or CCW direction. So I thought resistance and capacitance helped the motor driving.

  • 0 in reply to Yosuke Tezuka
    Prodigy 10 points

    The load is kind of big. 

  • 0 in reply to Yosuke Tezuka
    TI__Mastermind 37683 points

    Hi Yosuke,

    In my opinion, it would be easier to limit the inrush current with the ISEN resistor. Having the current limit right below the OCP threshold will prevent an OCP fault during the inrush or stall. It would be much more reliable than adding resistance and capacitors at the output.

    However, if you have already finalized your design then this will not be an option. Are you switching the control inputs? If so, I recommend slowly ramping up the PWM duty cycle up to the desired value. This will prevent the current from rising to fast during start-up.

    I don't think the solution you propose will be helpful. The inrush current will be higher due to the added capacitance on the output terminals. If you have a resistor that can dissipate the motor current, you can connect the resistor in series with the output terminals to limit the current. This is another way to reduce the inrush current but will require a big resistor specially if your load current is large.

  • 0 in reply to Pablo Armet
    Prodigy 10 points

    Hi Pablo,

    Thank you so much for your advice. Now I'm testing with placing the chip on a breakout board, so I can do anything. And DRV8251 is still alive. I feel it's a tough chip.

    Yes, I'm going to place ISEN resistor first. If it doesn't work well, and then I'm going to place the resistor in series to the output line.

  • 0 in reply to Yosuke Tezuka
    TI__Guru 55615 points

    Hello,

    Thank you.  We will wait for your results.  Please update this post with any additional questions.

    Regards,

    Ryan