".... The PLL is a frequency-to-voltage converter of a different type than we have met before."
**broken link removed**
"Q. How do you make a frequency-to-voltage converter?... Designing PLL systems is beyond the scope of this discussion, but if a 4000-series CMOS PLL, the 4046, is used just as a phase detector (its VCO’s transfer characteristic is not sufficiently linear), we can build the FVC shown here, with an AD654 VFC." http://www.analog.com/library/analogDialogue/Anniversary/3.html
Some 4046 circuits:
http://ampage.org/hammer/files/Marston's4046circuits.PDF
Quoted from **broken link removed**
"Also a cheeper way to convert F/V is by the PLL 4046. The signal input is driven by your signal and the dc output is taken from the VCO input after the RC filter. Very simple and accurate."
"The output from comparator 67 is next directed through frequency to voltage converter or demodulator 51. Frequency to voltage converter 51 is preferably a commercially available 4046 device sometimes referred to as a phase locked loop... The square wave input to converter 51 is transformed into a DC voltage output on line 83... The particular signal processing circuit shown in FIG. 3B uses only an analog output from device 4046..." US Patent#: 4568933 [Link To 4568933] (click Images at the top of the page to search for FIG. 3B)