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DP83822I: Can’t use the external power to center tap in Ethernet chip

Robert Eschbach
Expert 6695 points
Part Number: DP83822I

We’re using the "DP83822" of Ethernet chip and use the 1.8V external power(LDO Regulator) to the center tap of the Ethernet chip in our design.

But we have the LDO REGULATOR(1.8V) damage Issue from our field.

We can't apply the internal power source to the center tap of the Ethernet chip in our design.

 

 

I’d like to know why can’t use the external power to center tap in Ethernet chip?

If we use the 1.8V external power to the center tap, what kind of risk is it?

If you have the internal circuit or detail block diagram, Could you share it?

Is the internal structure as below?

(See attachment)DP83822I.pdf

  • 0
    TI__Mastermind 39755 points

    Hi Robert,

    You have to use external power to power the center tap of the Ethernet chip. You just need to ensure that the voltage is the same level as AVD or else you might run into some issues.

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 20 points

    Hi Robert,

    Thank you for your help.

    I'd like to get more detailed technical information to find the root cause.
    Could you provide me the internal circuit or detail block diagram of RD+, RD-, TD-,TD+ in DP83822?

    As you say, "else you might run into some issues.."
    What kind of issues is there?

    Thank you.

    Best Regards,

  • 0 in reply to Lee Jaejin1
    TI__Mastermind 39755 points

    Hi Lee,

    RD and TD are powered electrically off of the AVD rail. If the input power to the center tap is a different value from the AVD rail, the issue would be having two closely related parts of the circuit being powered off of two different rails, as this might over-volt or under-volt. What type of issues are you encountering with your design?

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 20 points

    Hi Gerome,
    We’re using the "DP83822" of Ethernet chip and use the 1.8V external power(LDO Regulator) to the center tap of the Ethernet chip in our design.
    But we have the LDO REGULATOR(1.8V) damage Issue from our field.

    Below is the connection circuit of our product for external LDO.
    We should reproduce the same symptoms of LDO Damage.
    Could you provide me the reenactment information or a detailed block diagram, principle of operation of ethernet?

    Thank you.

  • 0 in reply to Lee Jaejin1
    TI__Mastermind 39755 points

    Hi Lee,

    Are you powering AVD from the same power source? Each instance of "3.3V or 1.8V Supply" referenced in figure 33 should be connected to AVD. If not the same source, what is the power up sequence?

    Lee Jaejin1 said:
    Could you provide me the reenactment information or a detailed block diagram, principle of operation of ethernet?

    I am unsure what you are asking for here.

    Sincerely,

    Gerome