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Original question:

CCS/LAUNCHXL-F280049C: Faulty GPIO pin?

TMS320F280049C: GPIO23 - Low Drive Strength

Douglas Street
Prodigy 20 points

Part Number: TMS320F280049C

Hi There,

I'm observing a low drive strength on GPIO23 of my 280049C device in TQFP100 package. In particular, when sinking current, I'm seeing ~200uA over a 10k pull-down, which was directly measured, resulting in ~1V at the IO when being driven LOW.

I'm aware that this pin is used for a DC-DC converter, and have disable the "analog" function to allow it to operate as a normal GPIO. I have confirmed at a register level that the appropriate bits of the GPAAMSEL are set to '0', and have tried toggling the pin several times well after boot-up and configuration to see if that helped.

Here is my configuration of the pin:

Note that this pin is specified for 4mA source and sink capability, so I find this behaviour a bit perplexing:

This issue is absolutely critical and hitting an important programme, so would appreciate a fast response.

Thanks,

-Doug

  • 0
    TI__Guru 52040 points

    What is the connection you have on this pin?

    3.3V source connected to the GPIO through a 10kOhm resistor?

    Then the GPIO is in OUTPUT mode and pulled low?

    Any other connections or items I have missed?

    Nima

  • 0 in reply to Nima Eskandari
    Prodigy 20 points

    GPIO23 is connected to a high-impedance input of another device with a 10k pull-up resistor.

    I confirm there is no unexpected leakage onto the trace connected to GPIO23 by:

    • Setting GPIO23 to LOW, and confirming the usual ~1V
    • Externally shorting GPIO23 to GND via a 1k resistor and probe
    • Observing the expected ~280mV voltage on GPIO23 instead of the usual ~1V

    Essentially, GPIO23 has an output impedance of roughly 20k, instead of the expected 70R.

    Further, I have confirmed this over 3 different devices and boards.

    Regards,

    -Doug

  • 0
    Prodigy 20 points

    I believe I have found the issue: VDDIO_SW was not tied to VDDIO as specified in the datasheet, leaving the 2x pins associated with the internal DC-DC powered by leakage currents. Derp.

    Thanks for your prompt response Nima.