The .25 Vdd and the +0.8 thing I read as...

"For the full operating voltage range (not just 4.5 to 5.5 volts), the Vin HIGH minimum spec is (Vin*0.25) + 0.8 volts"


The Schmitt trigger input specs are 0.8 Vdd, or Vdd * 0.8, not .8 volts - this value seems kind of high to me...

Note that those values are the minimums, not the typical (unspecified) or maximums.

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