Help me set the VCO frequency on HCF4046

[jimiweber]

Help On 4046

Hi every one.
I'm working on designing a FSK modulator and demodulator.
There are many problems that I have, but most serious one is this IC, HCF4046 which is a PLL.
to set the VCO frequency, two resistors and one capacitor is needed, but my problem is that in the datasheet PDF that i have, there is no design combination for setting the VCO frequency.
I need it to oscillate in 1.0MHZ.
Thanks to all of your team.
also, If anyone can find the complete datasheet, send me.
here's the datashhet that I got from the internet:
**broken link removed**

 

[IanP]

Re: Help On 4046

All info is here:


Rgds,
IanP

 

[cdh7]

Re: Help On 4046

But the HCT4046 VCO seems to be different from the HCF4046. The HCF datasheet gives a maximum frequency of 1.4 MHz, whereas the HCT can do 17 MHz.

Can you figure out some component values just by experimenting?

Regards,
Chris

 

[jimiweber]

there are some Differences between 74HC4046 and HCF4046

Thanks, but I already have 74hc4046, and this one is a little different from HCF4046, for example, Vcc Max input for 74hc is 6volts, but in HCF and also some others, Vcc input max is 20volts.
also, I figured oscillator settings from 74hc4046 datasheet, but it doesn't work in HCF. it oscillates at around 20KHZ.

and yes, it's possible to figure out by experience, but because I need it urgent, I needed some help.
so if anyone can help me, I'd be thankful.

 

[jimiweber]

Didn't work

I can't even find the combination by experience.
it seems that there is no linear way in capacitance.
some body plz help me.

 

[FvM]

Re: Help On 4046

If you don't need the offset frequency feature, you can omit R2 and simply select R1/C1 according to the center frequency diagram
in NXP HEF4046B datasheet.

 

[jimiweber]

It worked

Thanks FvM, your help worked, although it didn't work without R2, and I found that R2=13KHZ would do the job.
CD4046 gives a DC output without R2.

Thanks Everyone.