Suboctave generator - 4013?

[Happy Harry]

Hi Tony:

If you get bad trigger on some chips... try adding a
small capacitor at the clock input... maybe 20-30pF.

This usually does it for me. I think some chips actually
see multiple clock transitions at this point... like too
fast rather than too slow.

Or do what you did... specify ONE manufacturer !

Not all CMOS are created equal.

Worst offenders are the counters with "Schmitt trigger" inputs...
some of them have the schmitt trigger AFTER an inverter... which
of course is the same as not having a schmitt trigger at ALL !!
check the data sheets carefully !!!

H^) harry


>From: "Tony Allgood" <oakley at techrepairs.freeserve.co.uk>
>Reply-To: "Tony Allgood" <oakley at techrepairs.freeserve.co.uk>
>To: "Synth DIY" <synth-diy at node12b53.a2000.nl>
>Subject: Re: Suboctave generator - 4013?
>Date: Thu, 18 Jan 2001 20:14:07 -0000
>
> >Anyone use 4013-based sub octave generators in their designs?
> >Drawbacks? Limitations?
>
>Actually I have had a problem when using one manufacturer's version of
>the IC in the TB3030. I use a comparator to square up the signal from
>the 'square' output of the TB3030 VCO and then a further spare CMOS nand
>gate to straighten the edges just in case. However some samples appear
>not to divide by two. This maybe because of the less than fast rise time
>at the clock input (don't believe this bit), or because set-up times are
>not being met. Early CMOS 4000 specs are a bit wayward for this. I think
>there's a bit in Horowitz and Hill about this very thing. Or maybe there
>is a runt pulse being delivered by the comparator as it swings
>through... either way I can't get my scope to detect either runt pulse
>or rise time error. I tell my customers to use the Motorola part,
>MC14013s, which seem to be used in many early 1980s synths and stomp
>boxes. I have had no trouble with the Motorola part ever, and
>fortunately, they seem to be the most common part.
>
>As a footnote, one customer did suggest to use a 2K2 resistor as the
>feedback path, not just a simple wire link. This would always create a
>delay in the feedback path compared to the clock rising edge. I have
>never tried it to see if it would work.
>
>Regards,
>
>Tony Allgood  Penrith, Cumbria, England
>
>Oakley Modular Synth and TB3030:
>www.techrepairs.freeserve.co.uk/projects.htm
>My music: www.mp3.com/taklamakan
>
>
>
>
>
>

_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com