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PCM1690: Appropriate Reset Operation

Hideki Hayashi1
Expert 8740 points
Part Number: PCM1690


Hi team,

I have a question about Vcc rising behavior.

Both Vcc will stay at 1.8V, then rise up to 5V as shown at the attached picture. After Vcc is stable at 5V, the reset operation in 7.3.5 of the datasheet has done.

Is there any problems of Vcc staying at middle voltage?

Regards,

Hideki

  • 0
    TI__Guru 55043 points

    Hi Hideki-san,

    I do not recommend this type of power up routine.  Having intermediate voltages or non-monotonic startup can potentially cause device initialization issues.  I am not aware of any specific startup issue with the PCM1690, so it is possible that this has no problem, but I do feel it is bad practice to allow it.  Could they implement some kind of voltage supervisor in their supply path to prevent this?  Otherwise, I recommend issuing a reset command via that control interface after startup.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    TI__Expert 8740 points

    Hi Paul,

    Does "a reset command", which you mentioned at last, mean the statement of 7.3.5?  If so, customer always do this,  the startup shouldn't cause any issues.

    But I will let customer know the other descriptions you wrote just in case.

    Thanks

    Hideki

  • +1 in reply to Hideki Hayashi1
    TI__Guru 55043 points

    I would not expect any issues if they assert RST low during startup, and then release the pin once the power is stable.  If they do not have control over that pin, then I recommend they use the software reset command.

    Thanks,

    Paul