[sdiy] Issue with CD4024 Ripple Counter

[Mike Bryant]

I think this highlights why it’s best to move onto more modern designs.  Some of the CD series ICs were designed as far back as 1968 by companies that no longer exist – RCA, the original Fairchild, etc.  Back then you expected ICs to not be exact equivalents, even sometimes from the same manufacturer.   I remember discovering that NatSemi had two LM361s that were almost chalk and cheese, and designing a circuit to handle both was quite problematic.

Fortunately we got rid of this stuff as semiconductor manufacture became more of a science and less of an ‘eye of newt’ art.

From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Ben Stuyts
Sent: 18 September 2021 15:49
To: tim102 at timstinchcombe.co.uk
Cc: synth-diy mailing list
Subject: Re: [sdiy] Issue with CD4024 Ripple Counter


On 18 Sep 2021, at 16:23, Tim Stinchcombe <tim102 at timstinchcombe.co.uk<mailto:tim102 at timstinchcombe.co.uk>> wrote:

The 4024 already has schmitt-trigger input. (Not on the reset line
though.)

Datasheet says unlimited rise/fall time is allowed.

I'd be a little hesitant to suggest that this is so for _all_ makes of
CD4024 chips - on this Fairchild datasheet the maximum 'input rise and fall
times' given suggest there is a limit that one is recommended to not exceed:

https://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/CD4024BC.pdf

$DEITY! That is confusing even more. And different timing again.

I was looking at TI and ON Semi:

https://www.ti.com/lit/ds/symlink/cd4024b.pdf?ts=1631976289114
https://www.onsemi.com/pdf/datasheet/mc14024b-d.pdf

which both have the Schmitt-trigger input. Fairchild doesn’t even mention it.

Ben

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