[sdiy] 4046 PLL Usage

[MBEDTOM at aol.com]

Yeah, 100% of the Motorola-brand 4046s worked on 50mv!  I tested 2 tubes of 
them (50 units) and all were okee-dokee on 50mv.

I wasn't worried about the change in amplitude for the product design I did.  
I ended up approving all the popular manufacturer's parts and simply changed 
the production spec for a level adjustment elsewhere in the system.  I had 
spec'd 200mv and there was plenty of reserve to simply have the level jacked up 
higher.  Cake.  Once in a while one gets to thumb their nose at Murphy ... but 
not very often!  Now the time I misread a spec sheet and put in a part that 
was 1.5 orders of magnitude too slow ... uh, never mind.  That didn't happen.  
It was only a dream.  Really.  Didn't happen! <grin>

Peace.
Tom Farrand


In a message dated 1/6/2006 11:11:04 AM Central Standard Time, 
harrybissell at prodigy.net writes:

> I think it would be wrong to call the input stage 'amplifier'... buffer
> is probably better as it would not have any gain.
> 
> The usual input voltage transition point should be 1/2Vdd... but the logic
> 'high' and 'low' levels from that point are not guaranteed.
> 
> You're lucky if you were really using  a 50mV signal... there is no 
> guarantee
> but if it works, it works.
> 
> The point of manufacturer differences is VERY important. Sometimes they
> make equivalent chips are ARE different.  One counter chip had an input
> with schmitt triggers on two inputs, which were then AND'ed. Another
> manufacturer used the AND gate first, and schmitt triggered the output.
> DUH... what good does the schmitt trigger do, if it is not the first
> stage.
> 
> Anyone using the 4046 would be wise to use a comparator or other signal
> conditioner to guarantee logic levels first, before the signal input... and 
> especially
> if using phase comparator II (which you all will :^)
> 
> H^) harry
> 
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