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

over 8 years ago

0 Devin Cottier over 8 years ago

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 Simen Biao over 8 years ago 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 Manoj Santha Mohan over 8 years ago 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 Simen Biao over 8 years ago in reply to Manoj Santha Mohan

Expert 1875 points

Dear Manoj & Devin,

Thanks for your answers.

Simen

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F28377D: TMS320F28377D GPIO inrush current issue