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Back to back MAC connection

mahesh gohil
Prodigy 190 points
Other Parts Discussed in Thread: DP83620, DP83825I

Hello TI team,

We are planning to connect two Eth transceiver MAC back to back, one TI Eth transceiver and another one from different MAC.

We are looking for the colored block suggestion and this to consider.

  1. Will the DP83620 work for this purpose ? Any other suggestion
  2. We need to operate that device into 10 Base T mode, will it support in this mode
  3. Any limitation need to consider
  4. Suggestion for the MDIO configuration 

We appreciate your support.

Thanks !

  • 0
    TI__Genius 9920 points

    Hi Mahesh,

    Is there a reason you have selected the DP83620? We have many new products out in the market such as the DP83825 which is a 10/100 PHY used for RMII interface. The DP83825I EEE supports 100-Mbps and 10-Mbps speeds. In 10BASE-Te operation, EEE operates with a reduced transmit amplitude that is fully interoperable with a 10BASE-T PHY

    Would this be of interest to your design?

    Thanks,

    Cecilia

  • 0 in reply to Cecilia Reyes
    Prodigy 190 points

    Hello Cecilia,

    Thank you for your quick response.

     DP83620 is not finalized, during quick search I could find it. We would like to explore more cost effective solutions. We will check into DP83825 device. 

    Please let us know if there is any application note to understand the back to back MAC connection and things need to consider while doing this.

    Thanks!

  • 0 in reply to mahesh gohil
    TI__Genius 9920 points

    Hi Mahesh,

    Could you explain to me more this application? Where exactly is the back to back MAC going to be and why do you need this? I am not sure if I am following properly perhaps pointing out where exactly in the block diagram in this is occurring will help me understand more and point you to the right resources.

    Thanks,

    Cecilia

  • 0 in reply to Cecilia Reyes
    Prodigy 190 points

    Please check above updated blocks. Below are the specific queries,

    1) suggestion for the block 2 eth phy

    2)  Que 1 from above block : Connecting block 1 and 2 MAC. Please let us know while connecting RMII of two PHY back to back what are the things need to take care. Please suggest if there is any application note or reference available. Is it possible to use processor MDIO line as shown in block diagram to configure it ? Or should be used these PHYs using default strapping options. please suggests.

    3) Que 2 from block diagram : What are the things need to take care while connecting block 2 and 4. Back to back phy differential pair connection on same PCB? Please share if there is any application note available.

  • 0 in reply to mahesh gohil
    TI__Genius 9920 points

    Hi Mahesh

    I will have to review internally and see if I can find some collateral for your queries.

    Let me get back to you in 1-2 days about this

    Thanks,

    Cecilia

  • 0 in reply to Cecilia Reyes
    TI__Genius 9920 points

    Hi Mahesh,

    My apologies on the delay. Here are the answers to your questions above:

    1. As I mentioned above I recommend using the DP83825 or the DP83826.

    2. Both devices support RMII back to back between PHYs as well as master or slave. This is found in Figure 17 of the datasheet which should help you in terms of the connections between both PHYs. We have the other configurations listed in the datasheet as well that you can refer to in terms of documentation. 

     

    3. For your connection between 2-4 you will be able to do a transformer-less connection or a capacitive coupling. This is our app note which will be able to help in terms of design:

    http://www.ti.com/lit/an/snla088a/snla088a.pdf

    We also have a similar e2e question in regards to this as well: https://e2e.ti.com/support/interface/f/138/t/880126