Phil Hobbs wrote:

On 10/15/2012 07:59 PM, Jim Thompson wrote:
Finally zeroing in on modeling the 74HC4046 after finding a
unpublished AppNote that gave more details on the innards. This is
what a fixed frequency looks like, simulation-wise...

http://www.analog-innovations.com/SE..._VCO_2_SIM.pdf

Comments? Scalings? (This is based on AppNote and Datasheets
claiming trip at VDD/2).

First release will be VCO only and will be in LTspice format. Once
you approve that, the PFD is virtually all logic.

...Jim Thompson

Different manufacturers give you a wide variety of ridiculously
nonlinear tuning curves for the VCO--the tuning sensitivity varies like
3:1, and the oscillator quits below about 0.7-1.1V (@VDD=5) depending on
the device.

Major deja-vu here :-) I used NXP's MS-DOS tool to cook up some values
but they where way off. Fortunately the circuit I tried the HC7046 in
is a one-off and not something that needs to go into production. I
have used PLLs before but never had so much trouble getting the
circuit going.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
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