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SN74AHC1G00-Q1: Schmitt Trigger Action described in the datasheet

Tobias Fernandes
Prodigy 100 points
Part Number: SN74AHC1G00-Q1

Hello Folks,

I have one question about logic gate (AND)

I have seen that in the datasheet is written:  "Schmitt Trigger Action at All Inputs Makes the Circuit Tolerant for Slower Input Rise and Fall Time"

But when i check the rest of the datasheet, it is not given the threshold window ( ΔVT Hysteresis) or any picture illustrating that. Is there any reason behind? 

Thanks in Advance!

Tobias

  • 0
    Guru 316690 points

    "Schmitt-trigger action" is not the same as a real Schmitt-trigger input.

    The AHC application report says:

    Input hysteresis of typically 150 mV is included in AHC devices, which ensures the devices are free from oscillations by increasing the noise margin around the threshold voltage during low-input transitions.

    The AHC Designer's Guide says:

    Hysteresis in the input circuit is intended only to process reliably signals that have a slew rate of <10 ns/V. With a signal swing of 5 V, this corresponds to rise and fall times of about 50 ns. If signals with considerably longer rise and fall times are processed, the specially developed Schmitt triggers, such as the SN74AHC(T)14, should be used. These components have a considerably larger hysteresis of about 800 mV at VCC = 5 V and, therefore, allow processing of very slow edges without any problems.

  • 0 in reply to Clemens Ladisch
    Prodigy 100 points

    Thank you for the fast reply