[sdiy] Issue with CD4024 Ripple Counter

Ingo Debus igg.debus at gmail.com
Sat Sep 18 12:59:56 CEST 2021


> Am 18.09.2021 um 06:08 schrieb David G Dixon via Synth-diy <synth-diy at synth-diy.org>:
> 
> The thing is, I'm developing a product for sale -- another one of my Sketchy Labs modules -- so it's important that I can rely on the chips I ultimately choose.  At this point, I would never sell a module with a CD4024 in it.

In this case, it seems a bit risky to me using chips from one manufacturer that worked *so far*, while you know that chips from another manufacturer don’t work. At least do some tests at different supply voltages and different temperatures.

A long time ago I designed a filter that latched up when overdriven if a TL074 from a certain manufacturer was used. With a TL074 from another manufacturer it didn’t latch up. The obvious choice was, only use the chips from the „good" manufacturer. This was going to go into series production. Luckily a few weeks later it turned out that the „good“ chips sometimes latched up too. And even more luckily I found a pin-compatible opamp that reliably did not latch up (much more expensive though).

Also, it seems a bit unlikely to me that counterfeit chips would cause such a behavior. Did I get that right, they do work as they should, they’re just triggering on the wrong edge? Sounds more like ringing or ground bounce or some similar nasty stuff to me.
As I wrote, I vaguely remember a similar triggering problem where I never found the exact reason. The triggering pulses did look good, at least on my old 16 MHz Hameg scope. I think I solved it with a cap to ground or something like that. But that was a one-off just for my own use. There would no big harm done if it stopped working one day.

Ingo


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