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Hi I want to use the TPIC6C595 in some project. Because my application needs to be very noise insensitive I am wondering whether the shift register uses Schmitt Trigger inputs for G, SRCK, RCK, CLR, SER IN. But after looking at the datasheet I could not find any information about that.

How Texas Instruments marks the type of inputs?

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It doesn't use schmitt trigger inputs on those pins. Look at the recommended input levels, they are fairly normal for some logic gates without schmitt trigger inputs.

  • VIH High-level input voltage 0.85 VCC minimum
  • VIL Low-level input voltage 0.15 VCC maximum

I also would suspect that if it did use schmitt trigger inputs it would mention this on page one of the data sheet. There would also be some mention of the input hysterisis voltage limits.

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Generally, Schmitt triggers are only useful for suppressing noise if the signal involved is a low-frequency one which spends a (relatively) lot of time near the transition point. This does not apply to digital signals being provided to a shift register, and if it does apply you're going to be in trouble no matter what you do. Since any reasonable clock will go from 0 to 1 in much less than a microsecond, with less than 100 nsec more likely, Schmitt triggers simply will not help with noise suppression. You need instead to start looking into shielding and twisted pairs.

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