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I'm trying to setup two 4060 counter ICs, to run from internal rc oscillator. The first one will be set to 32Hz, and its pin 3 output (which divides the input clock by 1024), will be fed to pin 11 of the other 4060 IC, so from the pin 3 of the second counter, I can have 32768 seconds delays.(that's 32x32)

Since I don't want to use another chip or a crystal, i need to setup the first 4060 ic to run at 32 Hz.

From datasheet, pins 9,10,11 are used to set a frequency. I can't understand what are the R2 and C2 mentioned ? What value should they be?

This is the datasheet text covering the rc oscillator: datasheet of 4060

I think I can use Rt=28.9k, and Ct=470nF From the formula I get: F = 1 ÷ (2.3 x 28900 x 0.00000047) which equals to 32.009 Hz

But I don't know if the conditions in datasheet are met or not. (R2 should be much greater that Rt , and Ct much bigger than C2)

IC part number : HEF4060BT by NXP View Datasheet

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  • \$\begingroup\$ please link to the manufacturer's version of the datasheet whenever possible ... alldatasheet.com should be linked only if manufacturer does not provide the datasheet \$\endgroup\$
    – jsotola
    Nov 21, 2022 at 0:44

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C2 (stray capacitance) would typically be a few pF (maybe 10pF if you're using a breadboard) so 470nF is much bigger in either case.

You can use an R2 of 200K or something like that.

Don't stress too much about the exact component values, the frequency is quite inaccurate on these things, maybe you'll get within +/-10% without adjustment. If you need accuracy or you need stability, use the tuning fork crystal option and more division.

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  • \$\begingroup\$ A watch crystal? (32768Hz) if going with such crystal, should I use a 100pF and a 22pF as the datasheet suggests, or use two 12pF as the crystal datasheet suggests? \$\endgroup\$
    – Bikay
    Nov 21, 2022 at 5:38
  • \$\begingroup\$ It's sized for about a 22pF crystal, which are not very available. You might have to experiment with it. I'd try halving the capacitors and double the series resistor and using an 11.5pF load capacitance crystal. Even if the load capacitance is off a bit it will be infinitely more accurate than an RC circuit. You just don't want to overdrive the crystal. \$\endgroup\$
    – Spehro Pefhany
    Nov 21, 2022 at 5:50

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