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SN74AHC1G08: What is the schmitt trigger action?

Kazuya Nakai59
Guru 20500 points
Part Number: SN74AHC1G08
Other Parts Discussed in Thread: SN74AHCT1G08, , SN74LVC7001A, SN74HCS08, SN74LVC1G97

Tool/software:

Hello guys,

One of my customers is considering using SN74AHC1G08 or SN74AHCT1G08 for their new products.

At this moment, they have the following questions.
Could you please give me your reply?

Q1.
SN74AHC1G08 datasheet says on page 1 "Schmitt-Trigger Action at All Inputs Makes the Circuit Tolerant for Slower Input Rise and Fall Time".
What is this Schmitt Trigger action? I think this doesn't mean Schmitt trigger input which has hysteresis between rising edge and falling edge because the device doesn't have hysteresis spec.

Q2.
The sentence about Schmitt-Trigger Action is not described in SN74AHCT1G08(TTL level input version of SN74AHC1G08) datasheet.
Does SN74AHCT1G08 not have Schmitt-Trigger Action?

Q3.
Do you have any recommended device with Schmitt-Trigger input which has same function as SN74AHC1G08/SN74AHCT1G08?

Your reply would be much appreciated.

Best regards,
Kazuya.

  • 0
    Guru 260500 points

    1. All modern logic families have a little bit of hysteresis at the inputs, but it's only 100 mV or so. Its only purpose is to work around the inductance of the pins and the bond wires, so there is no hysteresis that is guaranteed to be available for your circuit. And your edges are still required to be faster than the Δt/Δv limit. It is an implementation detail that has no effect on your circuit design.

    2. Both AHC and AHCT (and LVC/AUP/AUC etc.) have Schmitt-trigger action.

    3. The SN74HCS08 and SN74LVC7001A are four-channel devices. The SN74LVC1G97 has a different pinout. There is no Schmitt-trigger AND gate with TTL-compatible inputs.