[time-nuts] 4046 replacement

Richard (Rick) Karlquist richard at karlquist.com
Wed Apr 18 12:11:25 EDT 2018



On 4/18/2018 6:27 AM, Bob kb8tq wrote:
> Hi
> 
> If this is a new build, why use a 4046 in the first place? There are many newer parts
> that will do all sorts of things. If this is a repair of something that has been running
> for years, is it > 5V supply to the chips? If so, you are pretty much stuck with 4000
> series CMOS.
> 
> There are no fatal flaws in the 4046, but there are basic design limitations. Those
> have been well documented over the years and here on the list. Going to a better
> part is the answer for that stuff ( = get away from  any xxxx4046 IC).
> 
> Bob
> 

Any 4000 series CMOS, besides being extremely slow (prop
delay measured in MICROseconds), have a totem pole output
that momentarily short circuits the power supply when
switching and generates tremendous EMI.

I once wasted several weeks of time running down a spur
problem that I eventually traced to a 4XXX frequency divider.

Rick N6RK




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