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DP83822I: Regarding the operation when VDDIO and AVD drop to 3V due to a momentary power failure

Shinichi Inoue
Guru 21646 points
Part Number: DP83822I

Dear Specialists,

The customer is considering DP83822I and has a question.

I would be grateful if you could advise.

--

Currently, both VDDIO and AVD are using 3.3V.

-If the product is operating at 3.3V and the output is restored to 3.3V → 3.0V → 3.3V due to a momentary power failure, can the operation be maintained without any problem after the restoration to 3.3V?

We believe that there is no problem for the following reasons.

-Since the product is designed to operate at 1.8V or higher, we believe that the internal circuit will operate without problems if the power input of 1.8V or higher is maintained.

On the other hand, at the moment of dropping 3.3V, phenomena such as false signal detection and garbled output data may occur.

Are these correct?

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Expert 7040 points

    Hi Shinichi, 

    Is the power temporary disconnected or ramped to 3.0V in a controlled way? 

    VDDIO and AVD are designed to operate at multiple voltage levels, described in the recommended operating conditions table of the datasheet. If power is maintained and drops to 3.0V, this is still within the recommended operating conditions of the PHY in 3.3V operation. The PHY will function during this period. 

    If the power were to drop to 2.9V, for example, this would fall outside of the recommended operating conditions for 3.3V operation and the PHY may not function normally as a result. After the power is restored, initiating a Reset to the PHY, will reinitialize and the PHY will regain normal operation.

    Regards,
    Justin

  • 0 in reply to Justin Lazaruk
    Guru 21646 points

    Hi Justin,

    Thank you for your reply.

    The datasheet is only described recommended operating condition, 3.15V<AVD<3.45V and 3.15V<VDDIO<3.45V.

    I think 3V means 3.3V-10%. 

    Is the operating condition specified separately from this description?

    I appreciate your great help.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Expert 7040 points

    Hi Shinichi,

    I apologize for the error, you are correct. The Recommended Operating Condition is 3.15V<AVD<3.45V and 3.15V<VDDIO<3.45V. 

    In this case, we cannot guarantee how the PHY will operate when the supplies are 3.0V, it may range from packet errors to link drop, but this outside the validation conditions of the PHY. 

    When power is restored, a Reset to the PHY will reinitialize under the recommended conditions.

    Regards,
    Justin 

  • 0 in reply to Justin Lazaruk
    Guru 21646 points

    Hi Justin,

    Thank you for your reply.

    I understand 3.0V with VDDIO and VAD is not acceptable.

    I'll share your suggestion with the customer.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi