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TMS320F280039C: Two adjacent GPIO ports are shorted

Cherry Zhou
Mastermind 22235 points
Part Number: TMS320F280039C

Hi team,

As shown in the figure below, the DSP supply voltage is 3.3 V. This chip has two pins, 78 and 79, as output pins, which theoretically output PWM complementary signals. Due to solder failure, two pins have been shorted. This is where the 78,79 output signal high level is around 1.6V. 

As shown in the figure below, the yellow color shows the 78 and 79 port output waveform after the short. Why is the 78,79 GPIO port high only about 1.6V? 

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Mastermind 19795 points

    Hi Cherry,

    If the EPWM signals outputted complimentary signals while it was shorted, the pin absolute maximum current rating was likely exceeded and the pins may (likely) be damaged.

    Reason: When one pin drives high and another drives low, there is little-to-no resistance between them. Thus the pin driving high will source more current than the absolute max specification, and the pin driving low will sink more current than the absolute max specification.

    Thus, the pin(s) are likely damaged, and this particular chip should not be used in design.

    Regards,

    Vince

  • 0 in reply to Vince
    TI__Mastermind 22235 points

    Hi Vince,

    Thanks for your support.

    the customer would like to learn more about why the output high voltage is up to about 1.65V after a short circuit  which should theoretically be 3.3V? Is it related to the chip construction or the peripheral circuitry of the design? 

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Mastermind 19795 points

    Hi Cherry,

    As mentioned, the primary reason is the driver might be damaged. It should not normally output 1.65V. The absolute maximum rating of the pin was exceeded, probably for an extended and repeated amount of time. Therefore none of the values of the device are guaranteed any more once the absolute maximum is exceeded. In this case, the pin is likely damaged and can no longer output 3.3V.

    Regards,

    Vince