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SN74AUC244: Bi-directional buffer

Dave Chang
Expert 4095 points
Part Number: SN74AUC244
Other Parts Discussed in Thread: TXB0108, SN74AUC17,

Tool/software:

Hello support team,

My customer would like to use buffer/driver at SPI signal and eSPI signal. (1.8V, open-drain preferred.)

It seems that there would be the need of bi-directional requirement.

Based on the block diagram of our buffer, it seems that we only have uni-directional ones.

Please kindly suggest or recommend some part we could use. Thanks.

Best Regards,
Dave

  • 0
    Guru 279750 points

    For SPI, you can use any buffer.

    Bidirectional eSPI signals cannot be buffered, because when the voltages at the two sides are different, the buffer does not know which one should override the other. (SN74xxx254 transceivers require a direction control signal, which eSPI does not provide. Auto-bidirectional level shifters like the TXB0108 are not buffers.)

  • 0 in reply to Clemens Ladisch
    TI__Expert 4095 points

    Hello Clemens,

    Thanks for the reply.

    Based on your suggestion, there seem to be no buffer possible for eSPI signal? Or there would be some possible solution? Is SN74AUC17 an option?

    The reason why we are asking this one is that the Intel choose our SN74AUC244 as the solution for buffering eSPI signal, please see the ref schematic here.

    Is this the possible solution?

    Best Regards,
    Dave

  • 0 in reply to Dave Chang
    Guru 279750 points

    I do not see how that schematic could work. In Single I/O mode, eSPI has unidirectional signals, but DAT0 and DAT1 go in different directions (and DAT2/3 are not used). In Dual/Quad I/O modes, the DATx signals are bidirectional and cannot be handled by a unidirectional buffer like the '244.