enter image description hereCan someone please help me with selecting resistors and caps.

I have a PLL set up using a CD4046BE (PC2) connected to 2 x CD4017 decade counters to enable a x100 multiplier.

My input frequency range is 1Khz to 5Khz and I want to output 100Khz to 500Khz .

I have applied a few examples x10 schematics using 1x CD4017 which have worked well so my circuit is ok but it is the selection of resistor values and cap values for my low pass filter and VCO which I can't get right. I tried using some formulas and tables for the CD4046 but my math isn't great and the values I've tried haven't worked.

I have added my circuit with R & C values which enabled me to multiply an input of 1.2- 3.9Khz to 120-390Khz.

  • \$\begingroup\$ The chances of you get an answer will be higher if you post a schematic of the circuit that you are building. \$\endgroup\$
    – mguima
    Jun 3 '20 at 1:53
  • \$\begingroup\$ If you have a working x10 solution, you may be able to go without (significant) math to a x100 solution if your input signal is in the same frequency range. The extra 4017 divider will reduce the VCO frequency by a factor of 10. Increase the VCO frequency, and its sensitivity, by a factor of 10, so now the combined VCO and divider is the same sensitivity as it was for the x10 design. Don't touch the filter components, should just work. \$\endgroup\$
    – Neil_UK
    Jun 3 '20 at 6:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.