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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Fortunately we got rid of this stuff as semiconductor manufacture became more of a science and less of an ‘eye of newt’ art.<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Synth-diy [mailto:synth-diy-bounces@synth-diy.org]
<b>On Behalf Of </b>Ben Stuyts<br>
<b>Sent:</b> 18 September 2021 15:49<br>
<b>To:</b> tim102@timstinchcombe.co.uk<br>
<b>Cc:</b> synth-diy mailing list<br>
<b>Subject:</b> Re: [sdiy] Issue with CD4024 Ripple Counter<o:p></o:p></span></p>
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<p class="MsoNormal">On 18 Sep 2021, at 16:23, Tim Stinchcombe <<a href="mailto:tim102@timstinchcombe.co.uk">tim102@timstinchcombe.co.uk</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">The 4024 already has schmitt-trigger input. (Not on the reset line<o:p></o:p></p>
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<p class="MsoNormal">though.)<br>
<br>
<o:p></o:p></p>
<p class="MsoNormal">Datasheet says unlimited rise/fall time is allowed.<o:p></o:p></p>
<p class="MsoNormal"><br>
I'd be a little hesitant to suggest that this is so for _all_ makes of<br>
CD4024 chips - on this Fairchild datasheet the maximum 'input rise and fall<br>
times' given suggest there is a limit that one is recommended to not exceed:<br>
<br>
<a href="https://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/CD4024BC.pdf">https://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/CD4024BC.pdf</a><o:p></o:p></p>
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<p class="MsoNormal">$DEITY! That is confusing even more. And different timing again.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I was looking at TI and ON Semi:<o:p></o:p></p>
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<p class="MsoNormal"><a href="https://www.ti.com/lit/ds/symlink/cd4024b.pdf?ts=1631976289114">https://www.ti.com/lit/ds/symlink/cd4024b.pdf?ts=1631976289114</a><o:p></o:p></p>
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<p class="MsoNormal"><a href="https://www.onsemi.com/pdf/datasheet/mc14024b-d.pdf">https://www.onsemi.com/pdf/datasheet/mc14024b-d.pdf</a><o:p></o:p></p>
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<p class="MsoNormal">which both have the Schmitt-trigger input. Fairchild doesn’t even mention it.<o:p></o:p></p>
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<p class="MsoNormal">Ben<o:p></o:p></p>
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