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Signal level and pcb layout recommendation for RGMII signals

mans
Expert 1005 points

I am looking for more information on signal level (Is it LVTTL or LVCMOS or maybe something else? and what s the voltage level 3.3 or 2.5 or 1.8).

I am also looking for any recommendation for PCB layout for these signals? In my design, my PHY chip is on another board compared to processor board and the distance between processor and PHY chip is around 10cm and there is a samtec connector in between.

I am wondering if the above configuration would works. Is there any suggestion on how to achieve this?

  • 0
    TI__Guru**** 170625 points

    Mans,

    mans said:
    I am looking for more information on signal level (Is it LVTTL or LVCMOS or maybe something else? and what s the voltage level 3.3 or 2.5 or 1.8).

    It is LVCMOS. See DM814x datasheet, section 3.2.6 EMAC [(R)(G)MII Modes] and MDIO

    The EMAC0/1 pins in RGMII mode (see EMAC[0] RGMII Mode and EMAC[1] RGMII MODE) are supplied from the DVDD_GPMC I/O supply voltage.

    DVDD_GPMC is 3.3 V/1.8V Power Supply Voltage. See section 6.2 Recommended Operating Conditions:

    (1) LVCMOS pins are all I/O pins powered by DVDD, DVDD_GPMC, DVDD_GPMCB, DVDD_SD, DVDD_C supplies except for I2C[0] and I2C[1] pins.

    The DM814x device supports dual voltages on some of its I/Os. These I/Os are partitioned into groups, and each group has its own dedicated supply pins: DVDD, DVDD_GPMC, DVDD_C, and DVDD_SD. The supply voltage for each group can be independently powered with either 1.8 V or 3.3 V.

    You can connect the EMAC interface to an external PHY that can operate at IO level of 3.3V or 1.8V only (depends on the Gig PHY you are using). Just make sure that DM8148 EMAC power supply pins are connected to the correct voltage source. If you want to use 1.8V RGMII interface, EMAC supply pins need to be connected to 1.8V supply, if you want to use 3.3V IO, then connect DM814x EMAC supply pin to a 3.3V source.

    Best regards,
    Pavel