VCO

[Grant Richter]

>>Any one test'ed the 74HC7046/74HC9046,a new design of the old 4046PLL?

>The linearity may be bad with the 4046, but the real problem with the
>'portamento' effect will be the loop filter.  If the filter is set too
>low in freq, it will cause lag.  If set too high, it will cause a
>'sproinging' over-under-over-under shoot problem.  the characteristics
>of this may change slightly with better linearity, but the real
>problem is the filter.

The 470K/47K 0.1uF cap filter given in the applications manual is optimized
for audio. Believe me I played with those values till I was blue in the
face. The phase locked loops step nicely from two octaves below middle C to
two octaves above using the above values for loop filter. Adjusting the
main timing cap will give you better locking in low or high parts of the
range. A good technique is to monitor the voltage into the VCO control
terminal (pin 9?) and adjust the cap to get half the supply voltage at a
frequency which is the center of your range.