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SN74AXC8T245: replace SN74AXC8T245 with SN74LXC8T245

Robert Alfred Kecs
Prodigy 50 points
Part Number: SN74AXC8T245
Other Parts Discussed in Thread: SN74LXC8T245, , TXV0108, TXV0106, TXU0304, TXU0104, TXU0204

Tool/software:

Can i replace SN74AXC8T245 with SN74LXC8T245.

The last one seems better / faster. I need to shift mostly up from 1V8 to 3v3 and occasionally 5V.

The SN74AXC8T245 is currently used on a RMII bus, can the SN74LXC8T245 be used in this application too? regarding data rate it should be better. Is there a reason there are no RMII applications with this chip?

Same questions for RGMII 

Best regards,

Robert

  • 0
    Guru 295220 points

    The AXC is optimized for lower voltages, so at these voltages, it is faster.

    For RGMII, you usually want the fastest translator with the smallest skew, which is the TXV0106/TXV0108.

  • 0 in reply to Clemens Ladisch
    Prodigy 50 points

    here is a more precise explanation of the situation i am in:

    I have 4* logic LVLs  1V8 2V5  3v3  5v

    RMII /RGMII are on 1v8 and 3v3  here i need something that can do both up and down conversion

    Other fast signals are a mix , i must mention that the 5v ICs are 3v3 logic compatible BUT they output 5V.

    The SN74AXC8T245  does not support 5v input but it is ok for outputting at 3v3.

    The SN74LXC8T245 have input and output of 5V BUT i don't know IF i can also use it for RMII/ RGMII.

    Ideally i would only use 1 type of chip, and i was wandering if that chip is the SN74LXC8T245 ?

    I am also open for other options, preferably something that is a drop in replacement for the  SN74AXC8T245 ( that i am already using, DIR2 signal is not that important but the ability to change the direction of half the chip is also very desired.) 

    What do you think? Any recommendations that i should research ?

    Best regards,
    Robert

  • 0 in reply to Robert Alfred Kecs
    Guru 295220 points

    RGMII usually requires the TXV. 5 V requires the LXC.

    I would also recommend the TXU0104/TXU0204/TXU0304, but that would increase the number of chip types.

  • 0 in reply to Clemens Ladisch
    Prodigy 50 points

    Found this:

    https://www.ti.com/lit/ab/scea129/scea129.pdf?ts=1728386263831&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FSN74LXC8T245%253Fdcmp%253Ddsproject%2526hqs%253D 

    and according to the table on page 2 it seems i CAN use a SN74LXC8T245 for RGMII ( and RMII since it is slower )

    That document is from APRIL 2024 so I think it is recent enough to be relevant.