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Variance in min/max on TI 74LVC1G123

John Yurcho
Prodigy 35 points


I have a question
about the TI 74LVC1G123 and its input thresholds for the A and B inputs.
 The data sheet says that both the A and B inputs have hysteresis.
 However, the data sheet does not specify the input thresholds for those
pins as is normally done for an input with hysteresis.  Instead, the input
thresholds for those pins are specified as I would expect for a normal logic
input.
In other words, I expected to see values for Vt+ min/max and Vt- min/max as well as a minimum
guaranteed amount of hysteresis.  Instead, I see Vil max = 0.7Vcc and Vih
min = 0.3Vcc (for 5V power).  Those values are very different from the
input thresholds specified for the same type chip made by NXP (where hysteresis
is specified).

Can anyone shed light on the difference in values?

  • 0
    TI__Mastermind 46480 points

    This part does not have true schmitt trigger inputs so we did not spec VT. It will have about 50mv of hysteresis but it will still have rise and fall time limits specd in the datasheet.  We have a lot of parts with what we call schmitt trigger action which means they can except slower inputs and will filter some noise but they are not true schmitt triggers.  Tue schmitt triggers will have no requirement on rise and fall time on the inputs.

    I looked at the NXP part and they have true schmitt Trigger inputs on A and B pin.