SN74LVC1G07: Schmitt trigger input on SN74LVC1G06 but not SN74LVC1G07?

Jonathan9420

Expert 2056 points

Part Number: SN74LVC1G07
Other Parts Discussed in Thread: SN74LVC1G06, , SN74LVC1G17, SN74LVC1G14, SN74LVC1G99

SN74LVC1G06 is inverter with "Schmitt Trigger Action on All Ports".
SN74LVC1G07 is buffer but does not say Schmitt trigger.

Is this a mistake/omission in one of the datasheets or are they actually different?

over 7 years ago

0 Emrys Maier over 7 years ago

TI__Guru* 96681 points

Hi Jonathan,

Neither of these parts is a true Schmitt-trigger. You can tell by checking the Electrical Characteristics table -- a real Schmitt-trigger will have V_t+ and V_t- values given (such as SN74LVC1G14 and SN74LVC1G17 have).

The 'Schmitt-trigger action' they refer to is a tiny amount of hysteresis built into the inputs of a device that allow for a bit more flexibility on input signals than standard CMOS inputs. Both of these parts are built on the same technology, so the mistake was leaving off that feature on the front page.

Many manufacturers (including TI) take advantage of that tiny hysteresis and market it as "Schmitt-trigger action." If you have noisy or slow inputs, it's better to go with a real Schmitt-trigger instead.

0 Jonathan9420 over 7 years ago in reply to Emrys Maier

Expert 2056 points

Yeah, I read through a lot of datasheets and discovered the two kinds of "Schmitt input".

I was hoping to get away with one of these as a voltage detector but the threshold varies too much (1.50 to 1.87 V, for instance), and I can't find anything that has both Schmitt input and open drain, so I'll go with a (bigger, more external parts) comparator.

0 Clemens Ladisch over 7 years ago in reply to Jonathan9420

Guru 268120 points

To get a buffer with Schmitt trigger input and open drain output, use the SN74LVC1G99 with the O̅E̅ pin as input.

0 Jonathan9420 over 7 years ago in reply to Clemens Ladisch

Expert 2056 points

Thanks, that's a good idea. The thresholds are still too variable, though, so I'll go with the comparator. A tiny 4-pin comparator (power, ground, analog input, open-drain output) with built-in threshold would be ideal.

0 ShreyasRao over 7 years ago in reply to Jonathan9420

TI__Guru 57390 points

Thank you, Clemens , for your suggestion.I like that .

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SN74LVC1G07: Schmitt trigger input on SN74LVC1G06 but not SN74LVC1G07?