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DP83869HM: Impact of operation without 2.5V rail, power sequencing

Dallas Clow
Intellectual 360 points
Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869

Is there any potential damage possible from operating the DP83869 without the 2.5V rail present in a two-supply configuration?  Normal power-up sequencing is scope capture is below, but boards for a new design were powered up several times without the 2.5V rail present and to date are not operating correctly.  We're still working driver, etc. issues but want to ensure that there was no potential damage.

Also, is the 2.5V rise time below acceptable?  This initial rise is very quick, but the total rise time is greater than the minimum specified 0.5ms.

-Dallas

  • 0
    TI__Expert 5425 points

    Hi Dallas,

    For both two-supply and three-supply configuration, the 2.5V is absolutely necessary. Not having it will not damage the part, but the PHY will not function properly without it. Overall, the PHY will not turn on or turn on properly without the 2.5V rail.

    As long as the rise time is greater than 0.5ms, it is ok. However, I would make it slightly longer in case there is some variability. If the power sequence specifications are not met, there is a good chance the PHY will not function properly.

    Regards,

    Adrian Kam