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TMS320F28388D: GPIO source/sink current

Luke Chen
Expert 5090 points

Part Number: TMS320F28388D

Hi champs,

According to datasheet, both F2838x and F2837x devices support maximum source/sink current 4mA.

Please refer to below pictures, my customer uses GPIO10 to generate below PWM signal, the waveform F2838x device generated is different from F2837x device, looks like the GPIO source/sink current capability is different between these two devices.

Please advise your comments on this situation, thanks for help.

Regards,

-Luke

  • 0
    TI__Mastermind 19795 points

    Hi Luke,

    This may potentially be caused by board parasitics, given the very high frequency. Please provide the schematic (and layout if possible) of the pins where the waveforms above were taken, for both devices.

    I will contact the board design experts to provide details on how best to mitigate parasitics at this frequnecy range (40ns cycle time).

    Regards,

    Vince

  • 0 in reply to Vince
    TI__Expert 6020 points

    Hi Luke,

    From the waveforms, It seems the total capacitance on GPIO pin is different: F2838 has higher cap value so the rise time is taking longer time to charge.

    In addition to Vince comments: Which boards you are using EVMs (launch pad or Control card) or you have your own board? Let me know to further comment.

    I would recommend checking the total capacitance along the path on board. 

    Regards,

    Uttam

  • 0 in reply to Uttam Reddy Pailla
    TI__Expert 5090 points

    Hi Uttam,

    This is my customer's hardware, not TI EVM.

    So can we say we are sure there have no GPIO source/sink current difference between F2838x and F2837x devices?

    Luke

  • +1 in reply to Luke Chen
    TI__Expert 6020 points

    Hi Luke,

    As per DS: both devices have same GPIO source/sink current and PWM types used for both devices are similar as per migration guide. It shouldn't be a concern from device perspective. 

    Link: https://www.ti.com/lit/an/spracq1/spracq1.pdf

    The challenge might be with the customers board design considering they used similar oscilloscope and probe settings to compare. As suggested, I would recommend to get the schematics for both devices to understand the difference. This might be a board parasitic issue. 

    Thanks,

    Uttam