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Original question:

TPS65910: "SWIO" fails to start

TPS65910: "SWIO" fails to start

?? ??
Prodigy 30 points
Part Number: TPS65910
Other Parts Discussed in Thread: AM3352

Tool/software:

I asked the same question before, but it was locked so I started a new question.
----Previous question---------

When powering up, the "SWIO" voltage may not be output about once in 1000 times.
I am using a combination of AM3352BZCZ80 and TPS65910A31A1RSLR.
Is there anything that could be causing the startup failure?
Please let me know if there is anything that needs to be checked.
-Other voltages are output normally.
-When the output is NG, other power supplies also start up faster than usual. At this time, the rise slope is distorted.
-Forcing pin 1 of the TPS65910 to low will restore "SWIO".
-Pins 1, 40, 37, 45 of the TPS65910 are connected to the AM3352.
Pin 33 "PWRON" is open.
-----------
A new question has arisen during my research.
It is about the specifications of the PWRHOLD signal of "TPS65910".
I have attached the data specifications.
The VinH of the PWRHOLD signal is Min 1.3V, Typ VDDIO/VCC7, Max VCC7.
Typ VDDIO/VCC7 is the power supply.
VCC7 is a 3.3V input.
VDDIO is the 3.3V generated by VAUX33.
-Question: What is the actual VinH of the PWRHOLD signal? Is that so?
The PMIC_POWER_EN signal output from the AM3352 connected to the PWRHOLD signal is a 1.8V output.
Can the PWRHOLD signal be recognized as Hi for sure?
-Question: When I tested it, the PWRHOLD signal was not recognized as Hi when it was below 1.725V. Why is that?

*I am not fluent in English so I am using a translation. Please excuse any strange sentences.



  • 0
    TI__Mastermind 22120 points

    Hi,

    First question, can you share your schematic and a scope capture of the power sequence showing the SWIO behavior?

    Also, the last thread on this subject was posted a long time ago. Has this issue been going on the whole time since then or did this issue recently reappear? Why did this issue go quiet for a while?

    Regards,

    James

  • 0 in reply to James Steenbock
    Prodigy 30 points

    I've attached the schematic for the first question.
    The scope capture is too infrequent to capture.(about once in 1000).
    Also, it's not clear which signal is affecting it.
    *The circuit diagram "VFB3" has been made public, but I don't think it has any effect.
    This problem has been going on for a while and I have no idea what the cause is.
    This is why I am asking an additional question now.(PWRHOLD signal of "TPS65910")

  • 0 in reply to ?? ??
    TI__Mastermind 22120 points

    Hi,

    Based on what the datasheet says, the PWRHOLD VIH threshold can be as high as VCC7.

    If VCC7 is 3.3V then it follows that the VIH threshold could be closer to this value. I wouldn't expect it to be right up to the max (3.3V) but it could be higher than 1.8V.

    Regards,

    James

  • 0 in reply to James Steenbock
    Prodigy 30 points

    Hi,

    The PMIC_POWR_EN output from the AM3352BZCZ80 has an IO voltage of 1.8V. This is the AM3352BZCZ80 specification.
    Is it okay to directly connect the AM3352BZCZ80 to the TPS65910A31A?

    Regards,

    kouichi

  • 0 in reply to ?? ??
    TI__Mastermind 22120 points

    Hi,

    As far as I know, this should be fine. I am assuming you mean connecting the PMIC_POWR_EN output of the AM3352 to the PWRHOLD input of the PMIC.

    1.8V would put you well above the expected typical VIH level for PWRHOLD (VDDIO/VCC7 = 3.3V / 3.3V = 1). Also based on your testing, 1.8V seems to be sufficient for HIGH detection.

    Regards,

    James

  • 0 in reply to James Steenbock
    Prodigy 30 points

    Hi,

    According to the datasheet, VAUX33 (VDDIO) will not start if PWRHOLD is low.
    In this case, (VDDIO/VCC7 = 0V / 3.3V = 0). However, this cannot actually be calculated.
    In that case, does the minimum value of 1.3V not apply?
    I think the answers to the above questions are at odds between the datasheet and the actual results.
    >-Question: When I tested it, the PWRHOLD signal was not recognized as Hi when it was below 1.725V. Why is that?

    Regards,

    kouichi

  • 0 in reply to ?? ??
    TI__Mastermind 22120 points

    Hi,

    I'm not sure the exact reason for the threshold being 1.725V in your case but this seems to be within the datasheet spec window. I don't know how this relates to the VDDIO level before it powers up but if high detection is 1.725 then this is the target you need to hit for PWRHOLD.

    I won't be able to deep dive into this since it's an older part but on our EVM, we use either 1.8V or 3.3V for the PWRHOLD pull-up voltage. Both of these would exceed the VIH you are measuring.

    Regards,

    James