[sdiy] Hi frequency VC clock

[mark verbos]

hi all,

I’m making a new digital delay using some adaptive Delta type 1 bit techniques. I’d like a clock that can be swept from 250kHz to 3MHz without any glitches. 
I’m using a 74HC4046 and it is almost right, but it freaks out when the CV gets near zero and jumps down to a lower frequency. Is this normal? What am I doing wrong?
I have a 220p cap and a 10k on pin 11 and a 100k on pin 12.

Thanks for any insights…

Mark