Why don't all CD4000 chips have Schmitt inputs?

[Joerg]

Hi All,

Just out of curiosity: Why is it that flip-flops and other chips in the
CD4000 series are "schmitt-less"?

So far I design at least 80% of the stuff around 40106 chips, simply
because they interface to analog very well because of their Schmitt
trigger inputs. But making a flip flop always costs a third of the chip
plus two resistors, meaning valuable space. If the 4013, 40175 and all
those had Schmitts this would open a whole lot of applications. After
all, this stuff is never used on fast circuitry anyways. I'd be happy if
they left maybe one non-inverting buffer sans Schmitt so it could be
(ab)used as an analog amp.

Regards, Joerg

http://www.analogconsultants.com

 

[John Larkin]

On Fri, 01 Oct 2004 21:16:36 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hi All,

Just out of curiosity: Why is it that flip-flops and other chips in the
CD4000 series are "schmitt-less"?

So far I design at least 80% of the stuff around 40106 chips, simply
because they interface to analog very well because of their Schmitt
trigger inputs. But making a flip flop always costs a third of the chip
plus two resistors, meaning valuable space. If the 4013, 40175 and all
those had Schmitts this would open a whole lot of applications. After
all, this stuff is never used on fast circuitry anyways. I'd be happy if
they left maybe one non-inverting buffer sans Schmitt so it could be
(ab)used as an analog amp.

Regards, Joerg

http://www.analogconsultants.com

Schmitts are usually slow. They probably didn't want to give up the
speed on an entire logic family. 4000's are pokey enough already.

John

 

[Tim Wescott]

Joerg wrote:

Hi All,

Just out of curiosity: Why is it that flip-flops and other chips in the
CD4000 series are "schmitt-less"?

So far I design at least 80% of the stuff around 40106 chips, simply
because they interface to analog very well because of their Schmitt
trigger inputs. But making a flip flop always costs a third of the chip
plus two resistors, meaning valuable space. If the 4013, 40175 and all
those had Schmitts this would open a whole lot of applications. After
all, this stuff is never used on fast circuitry anyways. I'd be happy if
they left maybe one non-inverting buffer sans Schmitt so it could be
(ab)used as an analog amp.

Regards, Joerg

http://www.analogconsultants.com

If they did that, how would we make cheezy crystal oscillators?

Besides, when they first came out they were the only CMOS in town, and
probably needed to be as fast as possible.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Joerg]

Hi Frank,

HEF4013 has a schmitt trigger clock input. I believe there were some
other HEF4xxx chips that also use schmitt trigger inputs where you don't
expect them, but I am not sure which ones.


Thanks, I didn't know that. Have to check it out. I just wish Philips

would learn how to create a practical web site.

Regards, Joerg

http://www.analogconsultants.com

 

[nospam]

Joerg <notthisjoergsch@removethispacbell.net> wrote:

How many times have we seen articles about the demise of the CD series?

I haven't but then I don't read many. Probably written by someone who
thinks thing go obsolete because they are old - they don't.

Things go obsolete because the market disappears or because something
better replaces them. A limited market for some 4000 series parts will be
around for ages. There is little scope to improve the power consumption and
anyone wanting to go faster has had alternative logic families for years.

 

[John Woodgate]

I read in sci.electronics.design that Joerg <notthisjoergsch@removethisp
acbell.net> wrote (in <WYt7d.5420$nj.2038@newssvr13.news.prodigy.com&gt
about 'Why don't all CD4000 chips have Schmitt inputs?', on Sat, 2 Oct
2004:

Can you imagine that some engineers of the newer generation don't even
know the 4000 series? It blew my mind. Did they ever have to be within a
budget in their life?

Not only that but they are low-emission devices, mostly, which is a
great help in meeting EMC requirements.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Fred Bartoli]

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> a écrit dans le message de
news:5ah7gTCOboXBFwhT@jmwa.demon.co.uk...

I read in sci.electronics.design that Joerg <notthisjoergsch@removethisp
acbell.net> wrote (in <WYt7d.5420$nj.2038@newssvr13.news.prodigy.com&gt
about 'Why don't all CD4000 chips have Schmitt inputs?', on Sat, 2 Oct
2004:
Can you imagine that some engineers of the newer generation don't even
know the 4000 series? It blew my mind. Did they ever have to be within a
budget in their life?

Not only that but they are low-emission devices, mostly,

You mean those engineers ?


which is a

great help in meeting EMC requirements.

Enginnering-Marketing Compatibility ?


--
Thanks,
Fred.

 

[John Woodgate]

I read in sci.electronics.design that Joerg <notthisjoergsch@removethisp
acbell.net> wrote (in <_Jz7d.23154$QJ3.11061@newssvr21.news.prodigy.com>
) about 'Why don't all CD4000 chips have Schmitt inputs?', on Sat, 2 Oct
2004:

And I thought you meant "engineer meme content".

Then there's 'extraneous metaphysical commentary'. (;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Rich Grise]

On Saturday 02 October 2004 08:42 am, John Woodgate did deign to grace us
with the following:

I read in sci.electronics.design that Joerg <notthisjoergsch@removethisp
acbell.net> wrote (in <_Jz7d.23154$QJ3.11061@newssvr21.news.prodigy.com
) about 'Why don't all CD4000 chips have Schmitt inputs?', on Sat, 2 Oct
2004:
And I thought you meant "engineer meme content".

Then there's 'extraneous metaphysical commentary'. (;-)
--

Involving electromagnetic consciousness, I presume. ;-)

Cheers!
Rich

 

[Ken Smith]

In article <L5u7d.23108$QJ3.5145@newssvr21.news.prodigy.com>,
Joerg <notthisjoergsch@removethispacbell.net> wrote:
[...]

Well, power consumption on most CD4000 is pretty close to zilch. You can
have half a dozen of these chips, leave them on for a year and the
battery will still be as good as new.

This can save you from having a real power switch. I've seen a few
products where "OFF" only means that the display and other power hungry
stuff if off. All the CMOS logic can stay powered up. The controls can
be a membrane switch that could never pass enough current to actually run
stuff.

Even with 74HCXX parts you can leave power on them. The trick bit is to
make a 5V regulator that doesn't have much current draw. Since they work
down to about 2V, you can just use a JFET for the regulator in a home brew
project.


--
--
kensmith@rahul.net forging knowledge