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Analog PLL

Anthony Roberts14969
Prodigy 30 points
Other Parts Discussed in Thread: CD4046B

  I am trying to maintain a signal output at a particular frequency. In the control for this signal I want to use a PLL becasue it would seem a fairly simple design to use, compare the input to a reference signal (in the hundreds of kHz)  and output a control signal that I can use in a simple feedback loop. However the signals are sinusoids. I cannot find a currently produced monolithic PLL. They are all digital.When I shopped on TI's website, I found the CD4046A and B, I liked them because they were simple PLLs but they are intended for digital signals. HOWEVER, application report SCHA002A , "CD4046B Phase-Locked Loop: A versatile Building Block for Micropower Digital and Analog Applications", page 17, shows the CD4046B being used for FM Demodulation with analog signals. Does this mean I can use this PLL for my frequency control application? If not does anyone have a reccomendation. I've never worked with PLLs before and I'd prefer to keep the circuit analog.

  • 0
    Prodigy 30 points

    Anthony,

    I think you can still use the CD4046B for your application, as long as you can amplify and Schmitt trigger your analog input signal. For your output signal, you can use a Sine shaping Circuit if its absolutely necessary (check out some patents on google). Generally phase detection circuits will utilise digital techniques and you won't find chips on the market that will facilitate the use of analog inputs on their own.

    What are the specifications of your input signal?

    Cheers,

    -Moe

  • 0 in reply to Mohamad Susli
    Prodigy 30 points

    The input is a pure sinusoid that must track the resonant frequency of a circuit. Essentially the PLL is used to compensate for frequency drift. But I would like to minimize non-resonant frequencies as they will contribute to ineffieciences in the system.

    Thanks for your help btw.

    ~Anthony