CD4046B: Designing an autotune circuit with cd4046b

Pierluigi Vienna

Part Number: CD4046B
Other Parts Discussed in Thread: LM331

Hi,

Would be possible to achieve something like this with cd4046b ?

I'm trying to achieve the Buchla synthesizer style Phase lock circuit, which locks the main synthesizer VCO to an external audio input

over 5 years ago

0 Emrys Maier over 5 years ago

TI__Guru* 96591 points

Hi Pierluigi,
I don't think this is the type of PLL you're looking for.

This device specifically only handles square waves. I see it most often used for frequency modulation or demodulation of a square wave carrier.

0 Pierluigi Vienna over 5 years ago in reply to Emrys Maier

Intellectual 350 points

Thanks a lot for Your answer. I've already achieved the desired effect in digital domain, but in this design would be better to achieve that analogically.. Could you suggest me a ti device that could make me track an audio input frequency and output a voltage?
Thanks again for your time

0 Emrys Maier over 5 years ago in reply to Pierluigi Vienna

TI__Guru* 96591 points

I would think a circuit like that would be very complex -- probably consisting of many op amps and filters to isolate individual frequencies. You can try asking TI's opamp team -- just open a new thread and select any op amp part number to get their attention.

0 Pierluigi Vienna over 5 years ago in reply to Emrys Maier

Intellectual 350 points

Hi, i don't need to isolate any frequency from the audio input, but just get a voltage out that is proportional to the input frequency. We can read that voltage and then rescale it for our best use.. Somebody told me i could pick the the VCO voltage in to get that. What do you think of this approach?

0 kai klaas69 over 5 years ago in reply to Pierluigi Vienna

Guru 140200 points

Hi Pierluigi,

the LM331 could eventually be used for this.

See also this nice link:

www.electronicdesign.com/.../whats-all-frequency-voltage-converter-stuff-anyhow

Kai

0 Pierluigi Vienna over 5 years ago in reply to kai klaas69

Intellectual 350 points

thanks a lot Kai, finally some light! i've red application notes of lm331. said that we would need not more than 20-50 millisecond for the converter to set the output, do you have any reccomendations on the circuits shown in the pdf?

0 kai klaas69 over 5 years ago in reply to Pierluigi Vienna

Guru 140200 points

Ciao Pierluigi,

I think the LM331 is the only frequency to voltage converter which is precise enough to hit the correct note. This is of major interest when doing music, right? On the other hand, like all analog working devices it will need a certain settling time to fully settle to the end value. The settling time mainly depends on the frequency and it's always tricky to convert very low frequencies. Here, a digital method will clearly beat any analog solution...

I would just build up a circuit with the LM331 and experiment with it. I'm sure it will be good fun... :-)

Kai

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CD4046B: Designing an autotune circuit with cd4046b