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SN74CBTLV3257: Can it support ePSI spec?

Jim Tsai
Expert 4470 points
Part Number: SN74CBTLV3257
Other Parts Discussed in Thread: TMUX1574

Hi,

My customer is looking for eSPI MUX solution the max frequency is 66MHz..

Can SN74CBTLV3257 support eSPI MUC spec?

  • 0
    TI__Guru 52462 points

    Hi Jim,

    What signals are you trying to switch with eSPI? 

    Are you switching the MOSI/MISO/CS/CLK lines, CS lines, or are you also possibly switching the Reset/Alert pins?

    Also the bandwidth may be a little tight - I think that is more up to the designer choice, but I typically do  fundamental frequency * 3 for minimum bandwidth requirement. For 66MHz that puts it at 198MHz which is within the -3dB bandwidth range, but you are approaching the -3dB point at 198MHz. The TMUX1574 is a updated version of this part with a higher bandwidth to help negate attenuation due to higher frequencies.

    However another caveat is that when a channel is connected both of the switches mentioned can handle the eSPI specs when they aren't switching; however if you are trying to switch while data is being transferred there will be data loss because the transition times of the switches can cause dropped bits. This will depend on application how important that is.

    Please let me know what signals you are planning to switch, and we may have better switches available. 

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Expert 4470 points

    Hi Parker,

    Include of CLK, CS, IO[0:3] , alert and reset.

    If SN74CBTLV3257  is not suitable, could you please suggest solution to me, thanks!

  • 0 in reply to Jim Tsai
    TI__Guru 52462 points

    Hi Jim,

    The SN74CBTLV3257 is fine for this application. However, you will need 2 IC's for the application. We don't have an 8 channel 2:1, so I think this will be our best option. 

    As I mentioned before the only concern I have for the SN74 is that the bandwidth gets pretty tight and you might lose more of the signal than you expect. It shouldn't be a problem because we are over 3x the bandwidth, but the TMUX1574 is the alternative with higher bandwidth.

    If you need anything else please let me know!

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Expert 4470 points

    Hi Parker,

    Appreciate for your support~

  • 0 in reply to Jim Tsai
    TI__Guru 52462 points

    No Problem Jim!

    If you need anything else please let me know!

    Best,

    Parker