• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 33 subscribers
  • Views 308 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DP83869HM: LED Hard Strap Settings and Other Options

Harikrishnan Thangamani
Prodigy 60 points
Part Number: DP83869HM


Hi Everyone,

Application of the device: 100BASE-TX and 1000BASE-T Ethernet Interface (SGMII to Copper Interface)

Here are some of the queries in the device,

1) I am configuring the auto-negotiation feature through SMI Interface. So I am not using hard strap settings in LED pins.

If so, Can I use that pins for LED Driving alone ?

2) I am configuring the I/O voltage as 1.8V. I want to drive the LED in active low state. So I am pulling up the LED to 3.3V.

I want to confirm whether I can do that ? VDDIO 1.8V and pull up 3.3V

3) Follow up in Q.No.2, If I am connecting like that when high signal is provided by PHY what will happen is there any current flow through LED ? Is LED will be damaged ?

Please clarify my doubts as soon as possible.

Regards,

Harikrishnan T

  • 0
    TI__Mastermind 19250 points

    Hi Harikrishnan,

    Please find my comments below.

    Harikrishnan Thangamani said:
    If so, Can I use that pins for LED Driving alone ?

    Yes.

    Harikrishnan Thangamani said:

    2) I am configuring the I/O voltage as 1.8V. I want to drive the LED in active low state. So I am pulling up the LED to 3.3V.

    I want to confirm whether I can do that ? VDDIO 1.8V and pull up 3.3V

    PHY operates in 1.8V domain and can't be pulled up to 3.3V. The recommended way to use LEDs with 1.8V VDDIO is by using level shifters.

    --
    Regards,
    Gokul.

  • 0 in reply to Gokul Koraganji
    Prodigy 60 points

    Hi Gokul,

    Thanks for the immediate reply.

    I have one more query related to this device.

    As per design checklist the maximum routing length recommended for MII signals is 6 inches.

    Is this routing length applicable for SGMII MAC also ? Since it is high speed interface I have query on this one.

    If we are routing SGMII Signals to another PCB or Module Is it recommended if so what precautions needs to be taken ?

    Please resolve my queries as soon as possible.

    Regards,

    Harikrishnan T

  • 0 in reply to Harikrishnan Thangamani
    TI__Mastermind 19250 points

    Hello Harikrishna,

    SGMII being a high speed signal is not recommended to be routed more than 4 inch typically.

    This is not a hard requirement, but you will have to board level Signal Integrity simulations to check the performance.

    It is not recommended to route SGMII signals through connectors to another modules. Again, you can check the performance using SI simulations, and check if performance is okay.

    --
    Regards,
    Gokul.

  • 0 in reply to Gokul Koraganji
    Prodigy 60 points

    Hi Gokul,

    Thanks for the reply.

    One more query regarding power sequencing and MDI Signals.

    1. As per datasheet, 1.1V and 2.5V has to be turned on simultaneously. Is there any delay accepted between these rails ?

    2. On MDI Signals, Can we route the MDI signals from PHY to another PCB or Module through connector ?

    3. What is the Maximum routing length recommended for MDI Signals, As per design checklist it was 2 inches max. Can we go beyond that if so what is the limit ?

    Because Microchip application note AN2054 insist that distance between PHY and Magnetics can go upto 3 inches max is so it impacts routing length.

    https://ww1.microchip.com/downloads/en/Appnotes/00002054A.pdf

    Refer Page No 7

    Please confirm the routing length maximum for MDI signals.

    Regards,

    Harikrishnan T

  • 0 in reply to Harikrishnan Thangamani
    TI__Mastermind 19250 points

    Hi Harikrishna,

    Please find my comments below.

    Harikrishnan Thangamani said:
    1. As per datasheet, 1.1V and 2.5V has to be turned on simultaneously. Is there any delay accepted between these rails ?

    1.1V and 2.5V can come up with a delay of 50ms as long as VDDIO is ramped later than these power supplies. Skew of 50ms between 1.1V and 2.5V is acceptable.

    Harikrishnan Thangamani said:
    On MDI Signals, Can we route the MDI signals from PHY to another PCB or Module through connector ?

    It is not recommended to do so. Using connectors might violate PMA compliance requirements.

    Harikrishnan Thangamani said:
    What is the Maximum routing length recommended for MDI Signals, As per design checklist it was 2 inches max. Can we go beyond that if so what is the limit ?

    Same as above. You can increase the routing provided PMA compliance requirements are met. We have not conducted any compliance tests with routing longer than 2 inches.

    --
    Regards,
    Gokul.