[sdiy] Best way to interface 3V and 5V logic ICs on the same circuit ?

[Roy J. Tellason]

On Sunday 15 July 2007 13:43, René Schmitz wrote:
> jbv wrote:
> > What is the best way to interface different logic ICs on the same
> > circuit, some using 5V and others using 3V (like a uC using 3V
> > and a DAC or external RAM using 5V) ?
>
> HCT gates have TTL compatible thresholds, which you can drive with 3.3V
> logic. Interpose some HCT buffers and you're set.
>
> The other way round can be done with 1k series resistors and a shottky
> clamp diode to Vcc. (Most CMOS inputs can handle Vcc+0.6V) However speed
> might be impaired because of the higher impedance.
>
> Cheers,
>   René

Got a fair assortment of HCT parts available,  here:

http://mysite.verizon.net/rtellason/w4s.html

if anybody wants to take some of this stuff off my hands.

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