Re: 3.3V-5V level ****fters

Joerg schrieb:

> What's the jelly-bean level ****fter du jour, the most popular?
> 
> Need to ****ft three sigs 3.3V to 5V and another three 5V to 3.3V. Stuff 
> us analog dudes normally don't do. The TXB0104 looks ok, so does the 
> 74LVC4245. But the specs for both are horrible, incomplete at best. Not 
> much in drive levels mentioned, or just for one direction.

Any simple 74HCT gate will do the level ****fting from 3.3 to 5 V. I have
used 74HCT08 in such cases (noninverting). Really cheap also, plus many
sources.

For converting 5 to 3.3V, just use a 5V tolerant 3.3V logic family -
74LVC is fine for this, for three signals I would again use a single
74LVC08. Or simply add (large enough) series resistors if the 3.3V input
impedance is high and speed is not critical...

However, you can of course also use single transistors for level
****fting (common base circuit). Works fine, but with the additionally
required resistors (and assembly expense) it's not cheaper than using
the ICs mentioned above. However, you'd have more flexibility for
placement and routing.

Tilmann