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SN74AXC8T245: level shifter for differential RGMII interface

jaron yoo
Prodigy 20 points
Part Number: SN74AXC8T245

we are using 1.8 logic level and 3V3 logic level between two system and interface over RGMII interface. And need to support 800Mbps data rate at least.

Question are;

I think we have to use level shift for Tx/Rx Clock and Tx/Rx En but the others are all differential so I don’t think we have to use eight Rx/Tx differential data line. Is it correct?

If we have to use level shifter for eight data transmission line, please let me know why? And what issue happen w/o level shifter.

  • 0
    TI__Guru 61950 points

    Hi Jaroon,

    I have known the RGMII to be at 125Mhz or 250Mbps data rate but not at 800Mbps.

    SN74AXC8T245 cant support 800Mbps data rate for the 1.8 <>3.3V translation. We also do not have devices which can support differential signaling( +/ - ).

    considering Interface portfolio on different interfaces including differential signaling.

    The devices might not work without level shifter unless the threshold of the 3.3V devices are above 1.8V.