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I need to power a 5V LCD display from a 3.3V microcontroller. On my breadboard I used 74AHCT125 level shifters powered at 5V. This worked fine.

For the PCB version I have - mistakenly - ordered 74LVC125 chips. With a 5V power rail can I still use them (the data sheet seems to me ambiguous)?

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LVC inputs are 5V tolerant so they can be used as level shifters from 5V to 1.8-3.3V.

However power supply voltage is 1.65-3.6V so you can't power them from 5V. Although the absolute max rating for VCC is 6.5V... But even if you powered it from 5V and it didn't smoke, LVC (just like HC or AHC) has CMOS input thresholds, so with 5V VCC the 3V3 logic levels would not satisfy Vih properly.

So unfortunately the answer is no, AHCT was the correct choice for 3.3 to 5V translation due to input levels compatible with 3V3 logic...

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  • \$\begingroup\$ Thanks for the answer. I was confused in that the nominal voltage was between 1.65 - 3.6V, but the max. supply voltage was 6.5V. However, as you pointed out, the purpose of this chip is level shifting from 5V down to 1.8-3.3V and not the other way. Guess I’ll just have to reorder. \$\endgroup\$ Jan 19, 2020 at 17:13
  • \$\begingroup\$ Yes, if you power it from 5V, LVC will have input thresholds around midsupply which won't work with 3V3 logic levels. \$\endgroup\$
    – bobflux
    Jan 19, 2020 at 17:42

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