Inverter Squarewave Generator Symmetrical Correction

ci139

Joined Jul 11, 2016
1,452
Is there a better way?
what frequency(/range)
response time (if the frequency is tunable)
required stability
output loading (if you attached the unbuffered "CLK" line it will backward affect the frequency)

... that's why there are dedicated iC-s for such tasks ... http://www.ti.com/clocks-timing/generators/products.html ...

otherwise dividing your clock by 2 (supposedly) gives you 50% duty (which is not always the optimum ratio for driving devices ...)

or - trivia - you need to achieve same charge discharge times to integrating cap (the higher the frequency = more close to upper limit of the logic family -- the harder to achieve)
 
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ci139

Joined Jul 11, 2016
1,452
there is no die to get the channel specs for the 4069 but is one for the lower power 4049
if you combine it with the http://cmosedu.com/cmos1/ltspice/ltspice.htm
the extract from the http://cmosedu.com/cmos1/ltspice/LTspice_CMOSedu.zip (attached) modify it's W & L you may be able to reproduce the 4049 functionality from it's d/s diagrams Fig.7 Fig.8 ... +timings . . . maybe
CD4049-2-SF.png
about http://people.ee.duke.edu/~krish/teaching/Lectures/MOS.pdf
might be also for some help https://docplayer.net/55710201-Spice-model-for-nmos-and-pmos-fets-in-the-cd4007-chip-dr-lynn-fuller.html a P-Spice model but some of it may be adoptable for LT'
 

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Audioguru again

Joined Oct 21, 2019
1,479
The CD4069 has symmetrical low output current Mosfets.
The CD4049 has much more current when the output is low than the CD4069 and much more than when its output is high.
Therefore a CD4069 produces a symmetrical squarewave but the CD4049 does not.

Simulation models have only "typical" spec's and ignores minimum and maximum spec's that REAL devices have.
 

Audioguru again

Joined Oct 21, 2019
1,479
Some CD4069 ICs have a minimum threshold voltage and others have a maximum threshold voltage but most are perfect, look at the datasheet to see the range. Maybe yours was not "typical". I said the CD4049 is (usually) symmetrical but the CD4049 is never symmetrical.
Here are graphs on their datasheets:
 

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ci139

Joined Jul 11, 2016
1,452
there is Fig.7 in the HEF4069UB with the | IOH | ≈ | IOL | ( TC4069 )
versus
HEF4049B with the | IOH | < | IOL | ( TC4049 )

. . . found -- the 4069 die specs (last pg.)

i tried to fast match it , but i did something wrong = my model yet doesnot quite work how it should ... but , in principle it's done as below (solver=alternate)
-- the Min 6.2V is an arteffact

Dev - 11.png
 
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