[time-nuts] Clock level conversion 5V -> 3.3V

Mark A. Haun haunma at keteu.org
Tue Sep 30 22:11:59 EDT 2014


Hi Bob,

The OCXO is one of those 26-MHz ebay Pletronics from a couple years
back.  I would like to not degrade its close-in phase noise (quoted as
-100 dBc @ 10 Hz, -130 dBc @ 100 Hz).  Thinking about Said's suggestion
to phase lock a higher-frequency sampling clock to this, with a loop BW
somewhere in the 10-100 Hz range.

I have seen a resistive divider used in a similar application, but
wondered if I could save the couple dozen mA they were spending.

Mark

On Tue, 30 Sep 2014 20:18:56 -0400
Bob Camp <kb8tq at n1k.org> wrote:
> Hi
> 
> How quiet does it need to be?
> 
> Put another way - how good is the OCXO?
> 
> What frequency are we talking about? 
> 
> What is the phase noise “need” after you get to 3.3V (is there a
> system spec)?
> 
> Bob
> 
> On Sep 30, 2014, at 5:46 PM, Mark Haun <haunma at keteu.org> wrote:
> 
> > Is there a "best" way to do this without adding phase noise?  For
> > example, a 5V OCXO into an ADF4002, or a 3.3V or even 1.8V logic
> > input.  Is a resistive divider the way to go?
> > 
> > Mark
> > 
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