• State Resolved
  • +1 person also asked this people also asked this
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 84 subscribers
  • Views 980 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.

TMS320F28377D: TMS320F28377D GPIO inrush current issue

Simen Biao
Expert 1875 points
Part Number: TMS320F28377D

Hi,

SDFM uses F28377D PWM pin for 20 Mhz clock,

But this will have EMI issue,

To reduce EMI , place a capacitor on GPIO (as below picture)and let the CLK waveform smooth .

We know GPIO sink/source current is +4/-4 mA,

And the capacitor (ex:100pF) will generate an inrush current larger than 4mA.

Will  this situation make a GPIO life cycle issue?

thanks,

best regards,

Simen

  • 0
    TI__Guru 60865 points
    Hi Simen,

    The +/-4mA specification is an operating condition, so this just tells you how much current the IOs can drive and maintain their high/low voltage specifications.

    I think you want to look at the "Absolute Maximum Ratings":
    Output current : Digital output (per pin) : IOUT : –20mA to +20mA

    In any case, if you want to reduce EMI by slowing the edges a little bit, using a series resistor of maybe ~50ohms would be a better choice. The problem with adding a capacitor is that now each switching event requires more power to be dissipated (which could end up as EMI).
  • 0 in reply to Devin Cottier
    Expert 1875 points
    Hi Devin,


    In addition to more power to be dissipated, will there be a risk of GPIO lifetime?
    thanks,

    best regards,
    Simen
  • 0 in reply to Simen Biao
    TI__Guru 55700 points

    Simen,

    The pins will get damaged only when sink current exceeds 20mA. So, I don't think you should have any issues.

    Regards,

    Manoj

  • 0 in reply to Manoj Santha Mohan
    Expert 1875 points
    Dear Manoj & Devin,

    Thanks for your answers.

    Simen