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SN74LV1T34: a universal level translator (instead of HCT/LVC)?

Daniel Ka
Intellectual 497 points
Part Number: SN74LV1T34
Other Parts Discussed in Thread: SN74LVC1G17, , SN74LVC2T45, SN74LXC8T245, SN74LVC1T45

Hello,

for up-translating 3.3V to 5V signal levels, I've been using (A)HCT1g17 schmitt trigger (HCT: tpd < 20 ns, AHCT: tpd < 8 ns) and for down-translating 5V to 3.3V signals, I've been using SN74LVC1G17 (also schmitt trigger input, tpd < 5ns). I prefer the schmitt trigger input over a "simple" buffer so I don't have to worry about the edges of input signals (maximum "input transition rise or fall rate").

Now I found the SN74LV1T34 (tpd < 8 ns) which looks like it can be used as an universal level translator for at least 5 V and 3.3V. It has weaker output drivers (~ 7 mA) which might reduce overshoot. Marketing information states that "No need for damping resistor". However, it does not have a schmitt trigger input. The max. input transition time is 20 ns / V. That should be ok for signals generated by an MCU or UART.

Anything I overlooked that might prevent the use of the SN74LV1T34?

Thanks.

  • 0
    TI__Mastermind 24485 points

    Daniel,

    I don't believe so.

    As you mentioned, it is not a schmitt trigger input, so slow edges could cause oscillations on the output and other undesirable behavior.

    But if you need a device that is capable of up translating 3.3 to 5V or down translating 5V to 3.3V, then this device is capable of doing either based on the single VCC supplied.

    The idea is the same as the AHCT1G17 that you are using today for up translation in that the input threshold can tolerate 3.3V at the input and ensure it recognizes a high input signal.

    Note that any device that you use to do single supply up translation will come with an ICC current penalty. In that since you are not driving the input voltage all the way to the VCC rail their will be some additional DeltaICC current consumption, but this was the same case with the (A)HCT1G17 device that you would have been using.

    If you want the best signal integrity and the lowest current consumption, the best device to use would be a dual-supply voltage translator such as the SN74LVC1T45. or if you need multiple bits there is the SN74LVC2T45 and SN74LXC8T245.

    Michael

  • 0 in reply to Michael J Schultis
    Intellectual 497 points

    Thanks. I've sampled a number of  SN74LV1T34 and will compare them to the  SN74LVC1G17 is used so far.