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CD4046 PLL Spice Model or VCO Info Needed

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MrAl

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Hello there,


Does anyone have a spice model for this or similar chip?

The data sheets do not show enough information about the VCO part of the chip to accurately model it, so if you dont have the spice model you may have information about the VCO part of the chip and that would do nicely too.

The VCO depends on two resistors R1 and R2, but the exact function of these resistors (electrically not behaviorally) is not shown on the data sheet. What i know so far is they appear to set two current levels which are then summed and get to the capacitor C1 through some switching transistors, but the details of how the current is developed from the VCO input is not shown.

Thanks :)
 

ronsimpson

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groups.yahoo.com/group/LTspice/ I think you can find spice models here.

If you need to make the model; you can make a current to frequency oscillator. The current is (one of the resistors (don't which)) + the( VCOin/supply voltage) * the current in the other resistor.
 

ccurtis

Well-Known Member
Take a look at this reference, sht 5. May help to understand how the VCO works. ASC file here is an attempt to model the VCO (I can't vouch for its functionality): http://f1.grp.yahoofs.com/v1/QIy1UC...aQ2OYhc/ Lib/CD4046/CD4046_VCO_draft1_acz.asc

Edit: Sorry link does not work because it is dynamic to the Yahoo users group mentioned by ronsimpson. Join the group and look for file CD4046_VCO_draft1_acz.asc (I'm not sure if it is proper to cross post the file to here directly).
 

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MrAl

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Hi again,

Ron:
I went to Yahoo and could not find the file. I think it was removed or something.

ccurtis:
Hey that's pretty nice. Apparently that study was done by John Kut of Magdalene College. Many thanks to him, as that's the best information found to date, it was nice of him to publish that :)
He goes over the operation of the VCO by test and also shows what the internal schematic is *supposed* to look like, then explains why it cant be that way after all.
This could provide enough information to form a reasonable model of the VCO, which was the only remaining mystery about this 4046 chip.
Can i ask where you found this pdf (if you care to tell that is)?
Thanks again!
 
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ccurtis

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Can i ask where you found this pdf (if you care to tell that is)?
Sure MrAl, go to this link: http://www.datasheetarchive.com/ and type "AN/4046 application note pll" in the search box. A link to the document is near the bottom of the search result page. I'd post the link directly, but most of the links are dynamically generated, so are NG after the first serving.

Edit: This data sheet from one manuf of the HC4046 (See Fig 2, sht 9) also gives some details and partial schematic of the VCO section.
 

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MrAl

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Hi,

Thanks again. I've been looking at different data sheets now and find them all interesting. Slight differences sometimes.
 
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