XR2207 and XR2209 VCO chips

[BJ]

Rene Schmitz wrote:
> 
> At 11:18 27.01.99 -0800, you wrote:
> 
> >Secondly, they have linear frequency sweeps.  So 1V/oct. operation is out
> >(this is considered the biggest stumbling block).
> 
> The same is said for the LM566 (tri, square), but there are ways.
> I don't know exactly for the 2206, but it could be done similar:
> 
> The pin for the timing resistor really senses the current into (or out of)
> that pin, (i.e. the pin is held internally at some voltage and the current
> flows to ground, or the control voltage) so it is misusable as a current
> input, with the usual expo convertors.
> 
> See http://www.uni-bonn.de/~uzs159/vco_566.html
> for an example.
> 
> It *may* work similarly for the 2206, when pin 9 is left open and a current
> sinking expo convertor is connected to pin 8. pin 8 is held at 3V above
> ground. I have not tried it, but If I had some 2206s around I'd certainly
> try it. I did build the circuit on my website however, and the sweep range
> is more than sufficient (app. 1:10000 !) though the datasheet claims only
> 1:10, but this figure is only for voltage control in the normal
> applications, and with a resistor as current source!
> This VCO did track pretty good, for such a cheap thing.
> 

This is the same thing that you can do with the 4046 Vco, using
just a odinary expoconverter as Magnus once talked about some time ago!

But the 4046 is a current out device!

Any linearity specs for the 566?
How about the 567 PLL? any one tried that one?

BJ