pg: 8 fig: 13
http://www.ti.com/lit/an/snoa593b/snoa593b.pdf

I have been looking to build this circuit and on the schematic I looked at the optional (+N frequency to voltage divider), can anyone tell me what this is? And as it is optional what is its function as I want to use the circuit to convert frequency to voltage with a presition response time.

Anthony

 

Its optional extra, you can use a cd4017 decade counter or other ripple counter, there are other pll chips, CD4046, NE565.

 

I have been looking to build this circuit and on the schematic I looked at the optional (+N frequency to voltage divider), can anyone tell me what this is?

If this is what you're referring to:

The optional counter is used to lock on a multiple of the input frequency.

 

You would put a frequency divider chip (binary counter) there, if you wanted to measure frequencies lower than what the LM331 can operate at.

 

You would put a frequency divider chip (binary counter) there, if you wanted to measure frequencies lower than what the LM331 can operate at.

The 331 is equivalent to the Raytheon RC4151 - that may open up the search to a bigger resource of appnotes.

When a PLL is used for frequency conversion - a divider is used to put a divided down frequency on the phase comparator so the VCO has to go faster to keep up. That's the classic textbook example of using a divider to multiply frequency.

 

Hello,

The following page of the EDUCYPEDIA has some links with information on PLL' s:
http://educypedia.karadimov.info/electronics/pll.htm

Bertus

 

Remember, this is a PLL precision frequency to voltage converter. The "F input" is the frequency to be measured.

 

If this is what you're referring to:
View attachment 101141
The optional counter is used to lock on a multiple of the input frequency.

Yes thats it with the dotted line.

 

Thank you for these notes, just having a good read of the info.

 

So this can be used to translate the vco's frequency (with optionional outputs from s1 to s10 on the 4017) to the readable frequency limit of the lm311.

And I noticed fig 14 (pg9) on the original schematic improves frequency range.