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SN74AHCT1G14: VCC can work normally at 1.8v or 2.8v.

user6124773
Prodigy 230 points
Part Number: SN74AHCT1G14
Other Parts Discussed in Thread: SN74AUP1G14, SN74AUC1G14, SN74AHC1G14, SN74AUP1T14

Hi:

Here's how I use it:

We now need a 26M clock, with a range of 2.8v or 1.8v to test the effect respectively.The original crystal was 2.8v with no load, but when loaded, it will reach 1.0v.Due to the change of crystal material technology, it cannot be used.We wanted to do this by putting a buffer behind the crystal and then attaching the load.The crystal output is connected to A end, and the load is connected to Y end.

When we test VCC= 2.8v, the output at A end is 2.8v
However, according to the specification, the VCC is suggested to be 4.5~5.5, so it needs to be confirmed whether the VCC can work normally at 1.8v or 2.8v?
BR
zhang
  • 0
    Guru 280680 points

    The AHCT family is designed for TTL voltage levels.

    For symmetric CMOS inputs, use the AHC family (without "T": SN74AHC1G14), but it does not work below 2 V. At lower voltages, use the SN74AUP1G14 (low power) or SN74AUC1G14 (high speed).

    Please note that all logic gates expect a digital signal at the input. If the output of the crystal is a sine wave whose peak-to-peak voltage does not go beyond the worst-case switching thresholds, then you must use a comparator instead.

  • 0 in reply to Clemens Ladisch
    TI__Guru 58390 points

    Hi Zhang,

    The ST can tolerate the slow rising edge signals and can convert the sine wave to squarewave. You could consider using the SN74AUP1T14 which can work for 2.8Vcc.

  • 0 in reply to ShreyasRao
    Prodigy 30 points

    Hi, Shreyas:

    we found  with 

    SN74AHCT1G14 SOT-23-5 chip，when we use VCC（1.8V），Y is 1.8V，no clock 26MHz.

    we now change VCC back to 2.8V to check whether it is related to the VCC change.

     

    BR

    Zhu Caihua

  • 0 in reply to user5228108
    Guru 280680 points

    The SN74AHCT1G14 is not guaranteed to work at any VCC lower than 4.5 V.
    (The SN74AHC1G14 is not guaranteed to work at any VCC lower than 2.0 V.)

    The datasheets say this might not work. Your experiments have shown that it indeed does not work at 1.8 V. And even at 2.8 V, any little change in the environment might break it.

    Why aren't you replacing the AHC(T) with an AUC or AUP device?

  • 0 in reply to Clemens Ladisch
    Prodigy 30 points

    Dear  Clemens:

    Do  you have full part number of  AUC or AUP chipset? We will double check these two chipsets.

    We now input with 2.8V sine wave, but it cannot afford with 8 load. We try to add a buffer between crystal and load. 

    And the VCC we want is 2.8V or 1.8V. The output voltage we want is 1.8V or 2.8V。 Could you please give the chipset suggestion？

    Many Thanks for reply

    zhu caihua

    zhucaihua@zhigoumao.cn

  • 0 in reply to user5228108
    Guru 280680 points

    As already mentioned in my first answer: SN74AUP1G14 (low power), SN74AUC1G14 (high speed).

  • 0 in reply to Clemens Ladisch
    Prodigy 30 points

    Hi,Clemens:

    we try on board with SN74AUP1G14DCKR, the function is OK .

    if we use SOT-23 pack SN74AUP1T14DBVR can substitute to SN74AUP1G14DCKR.

    Thanks

    BR

    Chris