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Levelshifting 3->5V. Can I add a DC bias of 0.5v or so to the 5v input line to bring up the 3v signals?

Assuming it doesn't just line up correctly, eg: If my Vih is 3.6v on the 5v side, and my Voh is 3.3v on the 3v side.

By DC bias I mean connecting up a voltage divider giving 0.5v to the line connecting the 3v->5v.

I'm guessing this isn't done as it would drain power when the 3v line goes low, but if the divider is high enough resistance, that could be minimal?

1 Replies

steveastrouk (author)2013-01-21

No, you will run into the noise margin of the two systems.

What are you trying to do this for ? Logic level shifting ? If you use a 74HCT gate, you will find the input ranges from 3..5V tie up nicely.
Other than that, the proper answer is a logic level shifter, like the 74LVC245