[time-nuts] Clock level conversion 5V -> 3.3V

Hal Murray hmurray at megapathdsl.net
Wed Oct 1 03:10:50 UTC 2014

vesoares at deea.isel.ipl.pt said:
> I would suggest some 3.3V logic (inverter) gate with 5V tolerant inputs
> from Little Logic TI portfolio. There are buffered and unbuffered gate
> available. 

What's the advantage of a chip over a pair of resistors?

haunma at keteu.org said:
> I have seen a resistive divider used in a similar application, but wondered
> if I could save the couple dozen mA they were spending. 

Power might be one.  If it's a long enough run that you need a termination, 
then the power doesn't cost anything extra.  If it's only a few inches, you 
can use higher values of resistance to save the power.

For a given value of resistance and a specific chip, there should be some 
crossover frequency where the power of the chip matches the power of the 
resistors.  It might be fun to play with the numbers.

These are my opinions.  I hate spam.

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