Low jitter oscillators - special frequencies

[Hal Murray]

Most special order crystal oscillator packages now have a
PLL in them. When you order a special frequency, they take
an unprogrammed unit off the shelf and program in the PLL
parameters. Delivery in a few days.

The problem is that you get the jitter specs of the PLL rather than
the crystal. The jitter turns out to be important for high speed A/D
applications. It's probably important in most RF work too.

Anybody know a good place to get real crystal oscillators made to order
in small volumes? I need 10 or 20 but the first try came up with
a min order of 250. I'm expecting 10-12 week delivery. I can live
with that.

Many crystal/oscillator companies used to be in the business
of making small runs to a specified frequency. How many are
left?


Anybody familiar with the details of the PLL setup? I assume
somebody did the math and figured out what frequencies they
have to stock in order to cover all the target frequencies they
might want to produce. How many different frequencies do they
have to stock? What sort of ratios are they using in the PLL?

When did everybody switch to PLLs?

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[mc]

"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message
news:cu6o4e$7uk$1@theodyn.ncf.ca...

Just order crystals. Newcomers don't realize that up till thirty or
so years ago, except for a handful of frequencies, crystals were not a
commodity. They were ground on demand, and of course you paid for them.
The only mass-produced crystals were for frequencies that were used
a lot.

I agree. I remember when 3.58 MHz was the only commodity crystal...

So if the frequency you want isn't a common frequency, you send the specs
to a crystal manufacturer, and they grind a crystal for you.

And this costs only a few dollars.

 

[Marko]

Depending upon the frequency you need, try Pletronics. Part of the
problem is that they aren't interested in selling a few dozen or even
a few hundred. They will provide samples at no cost if you can
convince them there is some possibility of larger volume. This is
assuming you are dealing with a reasonable frequency for them.

Also, if it is possible to taylor your design to some common
frequency, you should have more options. Check Digikey for some
common frequencies.

What frequency are you looking for and what are your jitter specs?

Marko



On Sun, 06 Feb 2005 17:53:46 -0600, hmurray@suespammers.org (Hal
Murray) wrote:

Most special order crystal oscillator packages now have a
PLL in them. When you order a special frequency, they take
an unprogrammed unit off the shelf and program in the PLL
parameters. Delivery in a few days.

The problem is that you get the jitter specs of the PLL rather than
the crystal. The jitter turns out to be important for high speed A/D
applications. It's probably important in most RF work too.

Anybody know a good place to get real crystal oscillators made to order
in small volumes? I need 10 or 20 but the first try came up with
a min order of 250. I'm expecting 10-12 week delivery. I can live
with that.

Many crystal/oscillator companies used to be in the business
of making small runs to a specified frequency. How many are
left?


Anybody familiar with the details of the PLL setup? I assume
somebody did the math and figured out what frequencies they
have to stock in order to cover all the target frequencies they
might want to produce. How many different frequencies do they
have to stock? What sort of ratios are they using in the PLL?

When did everybody switch to PLLs?

 

[dd]

In message <v6mdnYh-ZKiXM5vfRVn-jQ@megapath.net>, Hal Murray
<hmurray@suespammers.org> writes

Most special order crystal oscillator packages now have a
PLL in them. When you order a special frequency, they take
an unprogrammed unit off the shelf and program in the PLL
parameters. Delivery in a few days.

The problem is that you get the jitter specs of the PLL rather than
the crystal. The jitter turns out to be important for high speed A/D
applications. It's probably important in most RF work too.

Anybody know a good place to get real crystal oscillators made to order
in small volumes? I need 10 or 20 but the first try came up with
a min order of 250. I'm expecting 10-12 week delivery. I can live
with that.

Many crystal/oscillator companies used to be in the business
of making small runs to a specified frequency. How many are
left?


Anybody familiar with the details of the PLL setup? I assume
somebody did the math and figured out what frequencies they
have to stock in order to cover all the target frequencies they
might want to produce. How many different frequencies do they
have to stock? What sort of ratios are they using in the PLL?

When did everybody switch to PLLs?

There is approx 10:1 price variation between crystals from Tiwan etc and

locally made in yhe US or UK.I was an XO designer for 25 years but all
by designd went to the Far East for volume manufacture.
Vectron and Fox make locally in the US but at a price.
I note that PLL is not the only means for flexibility there is also the
direct systhisis route which will provide better close in jitter but far
out sidebands.
Note also that the low cost crystals employ low Q quartz (generally)
which will influence close in noise.

--
dd

 

[Marc H.Popek]

Hal,

Can can make you real xtal oscillator on any (reasonable) frequency you
choose) and free running oscillator for the unreasonable choices

Marco
"Hal Murray" <hmurray@suespammers.org> wrote in message
news:v6mdnYh-ZKiXM5vfRVn-jQ@megapath.net...

Most special order crystal oscillator packages now have a
PLL in them. When you order a special frequency, they take
an unprogrammed unit off the shelf and program in the PLL
parameters. Delivery in a few days.

The problem is that you get the jitter specs of the PLL rather than
the crystal. The jitter turns out to be important for high speed A/D
applications. It's probably important in most RF work too.

Anybody know a good place to get real crystal oscillators made to order
in small volumes? I need 10 or 20 but the first try came up with
a min order of 250. I'm expecting 10-12 week delivery. I can live
with that.

Many crystal/oscillator companies used to be in the business
of making small runs to a specified frequency. How many are
left?


Anybody familiar with the details of the PLL setup? I assume
somebody did the math and figured out what frequencies they
have to stock in order to cover all the target frequencies they
might want to produce. How many different frequencies do they
have to stock? What sort of ratios are they using in the PLL?

When did everybody switch to PLLs?

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or
unsolicited
commercial e-mail to my suespammers.org address or any of my other
addresses.
These are my opinions, not necessarily my employer's. I hate spam.

 

[Hal Murray]

[from my message of a month ago - looking for non PLL oscialltors]

Anybody know a good place to get real crystal oscillators made to order
in small volumes? I need 10 or 20 but the first try came up with
a min order of 250. I'm expecting 10-12 week delivery. I can live
with that.

Thanks for all the comments and suggestions to roll my own...

I was looking for a half-size can because I wanted to change
frequencies on an existing design with a socket.


If companies make to-order crystals, why don't they also make
to-order oscillators? (maybe with slightly longer lead times)
All they have to do is make the crystal and drop it into an
osc package rather than a crystal package.



I got an email suggestion to:

Try Cal Crystal / Comclox (www.calcrystal.com).
They had what I needed in stock. Thanks.

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.