[sdiy] Another new hard to find part....

[Roy J. Tellason]

On Tuesday 06 July 2004 11:30 am, Scott Gravenhorst wrote:

> >What I don't understand is the point of numbers like 74HC4xxx,  where
> > they're (apparently?) giving you the function of a 4000 series part but
> > putting a 74 in front of it?  Maybe I'm just missing the point as I have
> > not yet seen a databook for these newer families.

> There are small differences.  For example, I just learned that the 74HC4046
> is basically the same as a CD4046, (micro power PLL), but the VCO in the
> 74HC part tops out at a much higher frequency.

Now that's an interesting tidbit!	:-)

> I haven't researched the whole family, but would guess that there are
> performance advantages of many 74HC parts over CD4xxxx.

I can find the occasional datasheet out there on the 'net,  but really 
probably should get my hands on a book that covers those parts...

> Also beware the power requirements.  Some of the 74HC parts are 5 volt
> limited.

Yeah,  _that_ makes no sense to me,  why the heck they'd do that!

> >And I remember reading somewhere that the whole 4000 series was going
> > away. Is this the case?  If,  as I have the impression of but am not
> > sure,  the 74HC and similar parts will only work with lots lower voltage
> > supplies,  that sure is going to limit some options.  I kind of liked the
> > idea of a logic family which would run on 15V or so,  and sometimes even
> > wished that it were higher! (Like being able to run something off a split
> > supply like what's typical for op amps.)

> Not only will CD4xxxx work to 15 volts (some parts to 18), they will also
> work down to 3 volts.

True,  though this isn't an area where I've taken advantage of it yet.

> I have run several CD4xxxx based circuits from +/- 8 volts without problems. 
> I just make sure all of the parts in the design are speced to 18 volts.

What's that,  the "B" series?