Peter L. Peres wrote:
>
> On Mon, 26 Aug 2002, Harold Hallikainen wrote:
>
> >I need to convert a couple 5V logic lines out of a PIC running on 5V to
> >3V levels to drive a MultiMedia card. I've seen some 3V PLDs that have
> >"5V tolerant" inputs. Does anyone know of a simple buffer like that? One
> >that I'd be able to power with my 3V supply, but drive the inputs with 0V
> >and 5V?
>
> If you do not use very fast outputs series resistors and fast zeners
> (tranzorbs or the clamp circuit I showed with a small mod) are all you
> need. 3V Voh from the MMC is within the permissible range for Vih on PIC
> inputs (unless it is a schmitt input).


Better to use 2 resistors, voltage divider style.
With values of 1k and 1.5k it will perform well at
PIC output speeds, better than a zener solution.

Like the zener solution it WILL allow bidirectional
comms (3v -> 5v) as long as the PIC input is TTL
type as Peter mentioned.
-Roman

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