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DP83822H: What is the behavior of RX_CLK/CLK_OUT signal(s) during a device.

Ronnie Wright
Prodigy 50 points
Part Number: DP83822H
Other Parts Discussed in Thread: DP83620, DP83630, TMUX121, SN74LVC1G3157

Tool/software:

During RMII master mode will the DP83822 RX_CLK/ CLK_OUT signals float (Hi-Z) during device reset? 

  • 0
    TI__Mastermind 30130 points

    Hi Ronnie,

    From the datasheet, RX_CLK will be pulled low during reset.

    For clarity, the RX_CLK signal is not used in RMII mode:

    There is no CLK_OUT signal on DP83822. Is a CLK_OUT signal needed for your design?

    Best,

    Shane

  • 0
    Prodigy 50 points

    Hello Shane

    I asked a question concerning the DP83822 part's treatment of the CLK_OUT/RX_CLK lines during reset, thinking that the DP83822 would treat the CLK_OUT/RX_CLK lines similar to the DP83620/30 P/Ns during a reset. We have a design that is going to use the DP83620 or DP83630 in RMII master mode. Not sure if any of the TI engineers have been able to confirm the behavior on a dev. kit or if the datasheet clearly states the operational intent.

     
    In RMII master mode, we are concerned about the 50M_CLK_REF (derived from either CLK_OUT / RX_CLK / TX_CLK) b/c it will arrive at a shared MCU pin. We were hoping that these pins (CLK_OUT / RX_CLK / TX_CLK) on the DP83620/30 float during a device reset. This was not clear in the datasheet. If these signals do not float during reset, can you recommend a TI mux/switch that has enough BW and low enough Ron so the 50M_CLK_REF is not distorted or experiences too much propagation delay?

    Thanks,

    R. Wright

  • 0 in reply to Ronnie Wright
    TI__Mastermind 30130 points

    Hi Ronnie,

    DP83822 has similar functionality to DP83620, however these are two separate parts. I cannot guarantee they will treat the CLK pins the same during reset.

    For DP83620, RX_CLK will operate at 25MHz in reset:

    To confirm the behavior of TX_CLK and CLK_OUT it would be best to evaluate this on a DP83620 EVK. I can look into getting one of these, however it will likely take a couple of weeks to arrive. Is there a timeline when you need this data by?

    Ronnie Wright said:
    can you recommend a TI mux/switch that has enough BW and low enough Ron so the 50M_CLK_REF is not distorted or experiences too much propagation delay?

    I've reached out to a member of the MUX team with this question and am awaiting a reply. It may be more convenient to create an E2E thread with this question to open a direct dialogue with members of our MUX team. For example, you can use TMUX121 as the part number.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    TI__Mastermind 30130 points

    Hi Ronnie,

    I received a reply from our MUX team, it seems SN74LVC1G3157 is a potential option for a single 50MHz RMII CLK signal. For more details/questions on this MUX, I recommend submitting a separate E2E ticket with this as the part number.

    Let me know if you have any questions on our ethernet PHYs and I will do my best to help.

    Best,

    Shane