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SN74LV1T34: Level Convertor Support

Gerald
Genius 9575 points
Part Number: SN74LV1T34
Other Parts Discussed in Thread: SN74LVC1G125, SN74LVC1G34, SN74LXC1T45, SN74LVC1G17, TXU0101

Hi Experts,

Our customer is interested in using SN74LV1T34QDCKRQ1, SN74LV1T34DCKR and SN74LV1T125DBVR in his application. 

In the product selection guide here, it has been mentioned that their input type is 'TTL-Compatible CMOS'. Does it mean that these products can down-translate 5V TTL to 3.3V CMOS and 1.8V CMOS? If yes, then please provide an application note or test report for the same if available. Thank you.

Best regards,
Gerald

  • +1
    TI__Mastermind 25290 points

    Hi Gerald,

    The capability depends on the below.

    Hence, they are compatible as the device can interface well similar to the datasheet spec for such levels. Please see differences between TTL and 5V CMOS for more info, thanks.

    Best Regards,

    Michael.

  • +1
    Guru 258710 points

    "TTL-Compatible CMOS" means that they can receive TTL signals (about 3.4 V) when supplied with 5 V; in other words, they can be used for up-translating from 3.3 V to 5 V.

    But this particular feature is not interesting for you; LV1T devices can also up-translate from many voltages, and down-translate from all voltages. See [FAQ] Can the input voltage (Vi) to my logic device be higher than the supply voltage (Vcc)?

    If you need only down-translation, but not up-translation, then you can also consider other logic families with overvoltage-tolerant inputs, e.g., LVC, AHC, LV-A, AUP, AUC.

  • 0 in reply to Clemens Ladisch
    TI__Genius 9575 points

    Hi,

    Thank you for the information. The customer application requires down-translation from 5V TTL to 3.3V CMOS and 1.8V CMOS.
    "TTL-Compatible CMOS" means that they can receive TTL signals (about 3.4 V) when supplied with 5 V.
    Does it mean that the product can only up-translate TTL input signals? Can it down-translate a 5V TTL signal to 3.3V CMOS or 1.8V CMOS , when supplied with 3.3V or 1.8V?

    Best regards,
    Gerald

  • +1 in reply to Gerald
    Guru 258710 points

    No, TTL signals are just one of the voltages that are supported; this feature does not exclude other applications.

    TTL signals do not have 5 V.

    The LV-1T device can down-translate 5 V signals, but you could also use any buffer with overvoltage-tolerant inputs, e.g., SN74LVC1G34/SN74LVC1G17/SN74LVC1G125. (The TXU0101 or SN74LXC1T45 also work, but would require two supplies.)