🚀 go-pugleaf

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?

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.