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Original question:

LSF0108-Q1: The A-side voltage

LSF0108-Q1: Please help to recommend an automotive qualified voltage translator

Arie Li
Expert 3390 points
Part Number: LSF0108-Q1
Other Parts Discussed in Thread: SN74LVC8T245-Q1, SN74AHC125-Q1, SN74AHCT125-Q1

Hi team,

i would like to find an automotive qualified voltage translator for below application, would LSF0108-Q1 be suitable here? The SPI data rate is around 5M. Could you please give some suggestion if you have better solution? Thank you very much.

  • 0
    Guru 243220 points

    The LSF can work. It is designed for open-drain signals, which means that it requires pull-up resistors and does not work if you need a pull-down resistor. Furthermore, for high frequencies, you need to have strong pull-up resistors that use lots of current.

    SPI has unidirectional signals, so it would be a better idea to use unidirectional or direction-controlled translators that have proper buffers.

    The SN74LVC8T245-Q1 is not suitable because it has only a single DIR input for all eight channels. You could combine multiple smaller translators, but then you would need at least four devices.

    I recommend one SN74AHCT125-Q1 running at 5 V for translating up (the TTL-compatible inputs allow 3.3 V signals), and one SN74AHC125-Q1 running at 3.3 V for translating down (it has overvoltage-tolerant inputs).