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Original question:

An Input only pin of this TMS5704357BZWTQQ1 controller have the capability to drive an output using JTAG?

TMS5704357BZWTQQ1: Output Glitch on Power/Up down

Athun Siva
Intellectual 340 points


We are concerned about the Microcontroller during power-up/down, could glitch the output that stims  our power monitor, resulting in the board not completing a successful power-up. Any assurances from TI for glitch-free power cycling?  Any common practices recommend, to prevent these types of glitches from impacting other HW operation?

  • 0
    TI__Guru 73216 points

    Hi Athun,

    The I/O pins are configured as inputs while nPORRST is low and immediately after nPORRST is released. There is no internal glitch filter on GIO pins. While nPORRST is low, both the input buffer and output buffer are disabled. 

    And in this state, we have to refer "default pull state" in datasheet to find out the default pull value.

    So, in the datasheet it is give that a default pull state value for each I/O pins as shown below.

    So, the corresponding pull state given by "default pull state" will be applied to the pin while nPORRST is low and immediately after nPORRST goes High. If you want other than default pull state while nPORRST goes low, then we have to use external pull resistors.

    --

    Thanks & regards,
    Jagadish.

  • 0 in reply to jagadish gundavarapu
    Intellectual 340 points

    Hi Jagadish, Thanks for the response. I got your point on default conditions when nPORRST is low. What will be the GPIO state if nPORRST is low and the Power supplies, Core VCC AND/OR VCCIO is ramping up or down (not within 1.2 or 3.3V range). Does that guarantee the default state. Please confirm.

  • 0 in reply to Athun Siva
    TI__Guru 73216 points

    Hi Athun Siva,

    Athun Siva said:
    What will be the GPIO state if nPORRST is low and the Power supplies, Core VCC AND/OR VCCIO is ramping up or down (not within 1.2 or 3.3V range). Does that guarantee the default state.

    Yes, it guarantees the default state.

    The "Default Pull State" is the state of the pull applied to the terminal while nPORRST is low and immediately after nPORRST goes High.

    As you can see in above pic, nPORRST is in active low state while core VCC AND/OR VCCIO is ramping up or down, so the default pull state will be applied to the terminal while this nPORRST is low as well.

    --

    Thanks & regards,
    Jagadish.