PLL recommendations?

Do you need an oscillator or a PLL? If you just need an oscillator, use one. If you need a PLL to lock to an external clock, you're going to have to supply more information.

Of great importance is the type of application. Do you need analog 80MHz with little phase noise, or digital

Rene

I have a clean reference frequency, and need to generate another which is at an irrational relation to the first. It is desirable for the PLL output to be as stable as possible. Loop response can be very slow, as the reference is stable, and will not be switched. A secondary requirement, however, is that it may be necessary to alter the generated frequency, depending on operating mode of the system. This would still not require a rapid response, however.

The primary concern will be long-term stability of frequency.

I need a PLL. I have a reference frequency, and need to generate another frequency related to it. Except for the frequencies involved, it is straightforward.

frequency related to it. Except for the frequencies involved, it is straightforward.

Ok, now we're getting somewhere. What's the exact input and output frequencies? Any idea as to phase noise requirements? What's your power and cost budgets?

Take a look at this one: CY22393. It goes up to around 200MHz, programmable and available from DigiKey for example.

You have the longterm stability of the source oscillator anyway. If your source clock is as accurate as 1e-8, then your derived clock will also be 1e-8, as a PLL does not add cycles.

The phase noise is a different matter altogether. There the phase noise of the VCO is the one that matters. You wouldn't want an external VCO, I guess. Have a look at the Cypress CY27EE16 clock generator, makes 200MHz. For lower phase noise, requiring an external VCO, the AD4001 from analog devices goes to 200MHz

Rene

In this case, I can probably use one of the Cypress clocks, but I will = have a look at the AD4001 anyway. Thanks!

programmable

Thanks! That looks like a good fit.

"William Meyer" ...

at an irrational relation to the first.

If the ratio is irrational, what M/N are you going to program?

Regards, Arie de Muynck

You know, I thought about that later, and realized I must have been thinking of something else at tht time. The ratio is, of course, rational, albeit somewhat awkward.