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CD4046B: Looking for a PLL

Shlomi Yehezkia
Mastermind 6150 points
Part Number: CD4046B
Other Parts Discussed in Thread: SN74LV4046A

Hi Team,

I am looking for a PLL that accepts a input of 210Hz.
I need the output to be 5 times the input (i.e 1050Hz).

I found CD4046B, can you please verify that the CD4046B is suitable to work at 210Hz input frequency and output a times multiplication?

Is there any reference design for the CD4046B?


please advise.
Thanks,

Shlomi

  • 0
    TI__Guru* 96591 points
    Hi Shlomi,
    I would only recommend the CD4046B if you need over 5V support (up to 18V logic). Otherwise I would recommend the SN74LV4046A. All of the "4046" function devices work the same way and are intended to be functionally compatible.

    These logic based PLLs typically use a simple 2-inverter oscillator design that can become unstable at low frequencies. There's no limitation for the timnig capacitor value (there are limits on the timing resistors), so you should be able to set the oscillator to operate at 210Hz center frequency, but I can't guarantee that the oscillator will be stable at that frequency. I can only guarantee what's in the datasheet -- and that's typically going to be in the MHz range. The equations given are very simplified and assume you're running at a relatively high speed -- at low frequencies there's a lot more factors involved that would make the equations get quite long and complex.

    I would recommend getting a few samples and an EVM to work with to see if it works for you. You might have to develop an external oscillator to produce the frequency you need. To get a multiply by 5 output, you will definitely need an external counter circuit .