seeking 2.5V, 100mhz clock source

J

John Williams

Guest
Hi folks,

I'm looking for a 2.5V, 100MHz clock source, preferably in a surface
mount package. Any part or supplier suggestions?

2.5V operation is my highest priority. Existence of an Australian
supplier would also be helpful!

Thanks,

John
 
On Thu, 20 Nov 2003 15:15:52 +1000, John Williams
<jwilliams@itee.uq.edu.au> wrote:

Hi folks,

I'm looking for a 2.5V, 100MHz clock source, preferably in a surface
mount package. Any part or supplier suggestions?

2.5V operation is my highest priority. Existence of an Australian
supplier would also be helpful!

Thanks,

John
Click to expand...
Um, how accurate? Must it be a crystal oscillator?

Why 2.5 volts? Clocking an FPGA or something?

John
 
On Thu, 20 Nov 2003 15:15:52 +1000, John Williams
<jwilliams@itee.uq.edu.au> wrote:

Hi folks,

I'm looking for a 2.5V, 100MHz clock source, preferably in a surface
mount package. Any part or supplier suggestions?

2.5V operation is my highest priority. Existence of an Australian
supplier would also be helpful!

Thanks,

John
Click to expand...
At 2.5V you might be better off using a clock synthesizer, with a
lower frequency reference clock. At first glance the Motorola MPC9350
looks interesting.


================================

Greg Neff
VP Engineering
*Microsym* Computers Inc.
greg@guesswhichwordgoeshere.com
 
John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in message

jwilliams@itee.uq.edu.au> wrote:

I'm looking for a 2.5V, 100MHz clock source, preferably in a surface
mount package. Any part or supplier suggestions?

2.5V operation is my highest priority. Existence of an Australian
supplier would also be helpful!

Um, how accurate?
Click to expand...
Well I'm not measuring the speed of light - but +/- 100ppm or so would
be good.
For any future critical time keeping applications I could use an RTC
chip or whatever.

Must it be a crystal oscillator?
Click to expand...
Not necessarily - just simple and stable - basically just solder it in
and off I go...

Why 2.5 volts? Clocking an FPGA or something?
Click to expand...
Precisely - and the IO bank onto which this clock comes is driving
some 2.5V DDR, so I don't have a lot of room to manoeuvre.

The FPGA is actually hosting a soft core microprocessor (running our
linux port no less!), so I'm just generating a processor clock with
it. The FPGA has a digital clock synthesiser inside it that I could
use, but I'd prefer not to "waste" one if I don't need to (since the
DDR drive logic needs a couple as well).

But I should ask... what are my options for simple and stable 2.5V
oscillators and lower frequencies (24Mhz, 66Mhz, ...)??

Thanks,

John
 
jwilliams@itee.uq.edu.au (John Williams) wrote in message news:<3a2cf4e1.0311202341.238a2bab@posting.google.com>...
John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in message

jwilliams@itee.uq.edu.au> wrote:

I'm looking for a 2.5V, 100MHz clock source, preferably in a surface
mount package. Any part or supplier suggestions?

2.5V operation is my highest priority. Existence of an Australian
supplier would also be helpful!

Um, how accurate?

Well I'm not measuring the speed of light - but +/- 100ppm or so would
be good.
For any future critical time keeping applications I could use an RTC
chip or whatever.

Must it be a crystal oscillator?

Not necessarily - just simple and stable - basically just solder it in
and off I go...

Why 2.5 volts? Clocking an FPGA or something?

Precisely - and the IO bank onto which this clock comes is driving
some 2.5V DDR, so I don't have a lot of room to manoeuvre.

The FPGA is actually hosting a soft core microprocessor (running our
linux port no less!), so I'm just generating a processor clock with
it. The FPGA has a digital clock synthesiser inside it that I could
use, but I'd prefer not to "waste" one if I don't need to (since the
DDR drive logic needs a couple as well).

But I should ask... what are my options for simple and stable 2.5V
oscillators and lower frequencies (24Mhz, 66Mhz, ...)??
Click to expand...
Farnell stock two 100MHz crystal-controlled oscillators in SMD
packages - order codes 316-0282 (from C-MAC) and 329-8504 (from
SaRonix). Both are intended to run from 3.3V supplies.

IIRR some low voltage FPGA's can tolerate input voltages that go
higher than their supplies, so you might not need to divide or diode
clamp the outputs.

At 100MHz, low-voltage differential signals (LVDS), which can be
terminated without dissipating too much heat, are an attractive
option, and some FPGAs offer inputs which can be configured to accept
such signals.

The C-MAC web-site

http://www.cmac.com/mt/databook/

lists SMD oscillators offering ECL and PECL outputs, which have the
right sort of limited voltage swing, but probably not at the right DC
level - you might be able to do something with capacitor or
transformer coupling. I'd use a couple of wide-band transistors in
SOT-23 packages(BFR92 for NPN, BFT92 for PNP) to do any necessary
level and amplitude switching, but I've done it before.

------
Bill Sloman, Nijmegen
 
John Williams wrote:
John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in message


jwilliams@itee.uq.edu.au> wrote:


I'm looking for a 2.5V, 100MHz clock source, preferably in a surface
mount package. Any part or supplier suggestions?

2.5V operation is my highest priority. Existence of an Australian
supplier would also be helpful!


Um, how accurate?


Well I'm not measuring the speed of light - but +/- 100ppm or so would
be good.
For any future critical time keeping applications I could use an RTC
chip or whatever.


Must it be a crystal oscillator?


Not necessarily - just simple and stable - basically just solder it in
and off I go...


Why 2.5 volts? Clocking an FPGA or something?


Precisely - and the IO bank onto which this clock comes is driving
some 2.5V DDR, so I don't have a lot of room to manoeuvre.

The FPGA is actually hosting a soft core microprocessor (running our
linux port no less!), so I'm just generating a processor clock with
it. The FPGA has a digital clock synthesiser inside it that I could
use, but I'd prefer not to "waste" one if I don't need to (since the
DDR drive logic needs a couple as well).

But I should ask... what are my options for simple and stable 2.5V
oscillators and lower frequencies (24Mhz, 66Mhz, ...)??

Thanks,

John
Click to expand...
This will do it:

http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/SAW_Products/SAW_Oscillators/displayItem?itemId=EG2021CA&categoryId=EEA.QD.SAW_Products.SAW_Oscillators

-or-

http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/SAW_Products/SAW_Oscillators/go/Resources/TestC2/EG2021CA

If you can't paste that link, then the P/N is EG-2021CA at:
http://www.eea.epson.com/go/EEA
 
Fred Bloggs wrote:

John Williams wrote:

I'm looking for a 2.5V, 100MHz clock source, preferably in a surface
mount package. Any part or supplier suggestions?

This will do it:

http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/SAW_Products/SAW_Oscillators/displayItem?itemId=EG2021CA&categoryId=EEA.QD.SAW_Products.SAW_Oscillators

-or-

http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/SAW_Products/SAW_Oscillators/go/Resources/TestC2/EG2021CA
Click to expand...
Looks like just what I need - thanks.

John
 
Fred Bloggs wrote:
John Williams wrote:

John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in
message

jwilliams@itee.uq.edu.au> wrote:


I'm looking for a 2.5V, 100MHz clock source, preferably in a surface
mount package. Any part or supplier suggestions?

2.5V operation is my highest priority. Existence of an Australian
supplier would also be helpful!



Um, how accurate?



Well I'm not measuring the speed of light - but +/- 100ppm or so would
be good.
For any future critical time keeping applications I could use an RTC
chip or whatever.


Must it be a crystal oscillator?



Not necessarily - just simple and stable - basically just solder it in
and off I go...


Why 2.5 volts? Clocking an FPGA or something?



Precisely - and the IO bank onto which this clock comes is driving
some 2.5V DDR, so I don't have a lot of room to manoeuvre.

The FPGA is actually hosting a soft core microprocessor (running our
linux port no less!), so I'm just generating a processor clock with
it. The FPGA has a digital clock synthesiser inside it that I could
use, but I'd prefer not to "waste" one if I don't need to (since the
DDR drive logic needs a couple as well).

But I should ask... what are my options for simple and stable 2.5V
oscillators and lower frequencies (24Mhz, 66Mhz, ...)??

Thanks,

John


This will do it:

http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/SAW_Products/SAW_Oscillators/displayItem?itemId=EG2021CA&categoryId=EEA.QD.SAW_Products.SAW_Oscillators


-or-

http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/SAW_Products/SAW_Oscillators/go/Resources/TestC2/EG2021CA
Click to expand...
I just noticed that these devices are due for mass production in Spring
2004, given the small numbers we'll be wanting, I wouldn't expect to get
some any time soon.

So, falling back to al ower frequency, but still on 2.5V.. It is stated
explicitly in the Xilinx data sheets not to drive an input above it's
rated voltage - so I'm not happy about using a 3.3V clock.

So, any 2.5V oscillators at 25-66Mhz?

Thanks,

John
 
On Tue, 25 Nov 2003 11:50:40 +1000, John Williams
<jwilliams@itee.uq.edu.au> wrote:

Fred Bloggs wrote:


John Williams wrote:

John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in
message

jwilliams@itee.uq.edu.au> wrote:


I'm looking for a 2.5V, 100MHz clock source, preferably in a surface
mount package. Any part or supplier suggestions?

2.5V operation is my highest priority. Existence of an Australian
supplier would also be helpful!



Um, how accurate?



Well I'm not measuring the speed of light - but +/- 100ppm or so would
be good.
For any future critical time keeping applications I could use an RTC
chip or whatever.


Must it be a crystal oscillator?



Not necessarily - just simple and stable - basically just solder it in
and off I go...


Why 2.5 volts? Clocking an FPGA or something?



Precisely - and the IO bank onto which this clock comes is driving
some 2.5V DDR, so I don't have a lot of room to manoeuvre.

The FPGA is actually hosting a soft core microprocessor (running our
linux port no less!), so I'm just generating a processor clock with
it. The FPGA has a digital clock synthesiser inside it that I could
use, but I'd prefer not to "waste" one if I don't need to (since the
DDR drive logic needs a couple as well).

But I should ask... what are my options for simple and stable 2.5V
oscillators and lower frequencies (24Mhz, 66Mhz, ...)??

Thanks,

John


This will do it:

http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/SAW_Products/SAW_Oscillators/displayItem?itemId=EG2021CA&categoryId=EEA.QD.SAW_Products.SAW_Oscillators


-or-

http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/SAW_Products/SAW_Oscillators/go/Resources/TestC2/EG2021CA

I just noticed that these devices are due for mass production in Spring
2004, given the small numbers we'll be wanting, I wouldn't expect to get
some any time soon.

So, falling back to al ower frequency, but still on 2.5V.. It is stated
explicitly in the Xilinx data sheets not to drive an input above it's
rated voltage - so I'm not happy about using a 3.3V clock.

So, any 2.5V oscillators at 25-66Mhz?
Click to expand...
John, maybe I'm missing something here. Why not use a simple level
translation stage (one transistor) or even a level clamp? That way,
any TTL oscillator source can be used.
 
So, falling back to al ower frequency, but still on 2.5V.. It is stated
explicitly in the Xilinx data sheets not to drive an input above it's
rated voltage - so I'm not happy about using a 3.3V clock.

So, any 2.5V oscillators at 25-66Mhz?
Click to expand...
It sounds like you have a 3.3V supply handy. What's wrong with
a simple resistive divider?

I'd also be looking at something like AC coupling LVPECL.

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