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Harris / DM8168 / NMI pin short

Tim Sloper
Intellectual 1750 points
Other Parts Discussed in Thread: UCD9222

Factory Apps,

 

Would you please review the e-mail below from an engineer at Harris and comment?

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  1. We are trying to isolate when the issue occurs.  We check the NMI pin prior to applying power, there is no short.  In order to program the UCD9222 device, the +3.3V is on. All other voltages to the DM8168 processor are off.  After programming the UCD9222, power is applied with the normal sequence: 3.3V, CVDD (1-V AVS) ,1-V Constant, 1.8V, 1.5V, 0.9V.  JTAG testing reveals a short at that port.  Power is removed to measure the NMI pin to ground and +3.3V plane.  Five (5) cards have failed with this issue.  Three (3) of the 5 the NMI is short to ground and two (2) of the 5 are short to +3.3V plane.

Why this pin? The pin is externally pulled up to +3.3V through 10k resistor.  This is why I am asking for the IO structure behind the pin.

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Thank you,

Tim

  • 0
    TI__Guru**** 170625 points

    Hi Tim,

    The NMI pin is (by default): active low, input, internal pull-up enable, 3.3V. Check register PINCTRL317 (at address 0x48140CF0).

    From what I understand, by some reason you make this pin external pull-up to 3.3V through 10k resistor. If you need to keep the external pull-up solution, I think you should disable the internal pull-up. You can do this in PINCTRL317[3] PULLDIS bit, write 0x1 in it.

    For detailed information about internal versus external pull-up/down design, check DM816x datasheet, section 4.3.1 Pullup and Pulldown Resistors

    Regards,

    Pavel