oN 24-Jan-04, Arie de Muynck said:

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

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.

-- 
Bill
Posted with XanaNews Version 1.16.1.2

"William Meyer" ...
> I have a clean reference frequency, and need to generate another which is
at an irrational relation to the first.


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

Regards,
Arie de Muynck

oN 22-Jan-04, Andras Tantos said:

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

Thanks! That looks like a good fit.

-- 
Bill
Posted with XanaNews Version 1.16.1.2

oN 22-Jan-04, Rene Tschaggelar said:

> 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

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

-- 
Bill
Posted with XanaNews Version 1.16.1.1

William Meyer wrote:
> oN 22-Jan-04, Rene Tschaggelar said:
> 
>>Of great importance is the type of application.
>>Do you need analog 80MHz with little phase noise, or digital
>>80MHz just as clock. What would be the input ?
>>Another XCO ?
> 
> 
> 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.


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
-- 
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

> I need a good PLL, and the frequency I need to generate is well beyond
> the range of any 4046 type device. In particular, I have a need for
> almost 80MHz. Any recommendations? I'm looking for inexpensive, small
> parts count, and CMOS.
>


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

-- 
Regards,
Andras Tantos
<http://andras.tantos.homedns.org>

William Meyer wrote:

> oN 21-Jan-04, Jim Stewart said:
> 
> 
>>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.
> 
> 
> 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.

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?

oN 22-Jan-04, Rene Tschaggelar said:

> Of great importance is the type of application.
> Do you need analog 80MHz with little phase noise, or digital
> 80MHz just as clock. What would be the input ?
> Another XCO ?

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.

-- 
Bill
Posted with XanaNews Version 1.16.1.1

oN 21-Jan-04, Jim Stewart said:

> 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.

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.

-- 
Bill
Posted with XanaNews Version 1.16.1.1

William Meyer wrote:
> I need a good PLL, and the frequency I need to generate is well beyond
> the range of any 4046 type device. In particular, I have a need for
> almost 80MHz. Any recommendations? I'm looking for inexpensive, small
> parts count, and CMOS.
> 


Of great importance is the type of application.
Do you need analog 80MHz with little phase noise, or digital
80MHz just as clock. What would be the input ?
Another XCO ?

Rene
-- 
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net