Author Topic: CMOS logic OCXO to LVDS converter without adding too much jitter  (Read 1450 times)

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Offline twitzelbosTopic starter

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Dear all,

I hope this question hasn't been asked too often before, but I'm hoping this has a very simple answer. I'm trying to convert the output of a CMOS digital output OCXO module to LVDS without adding a lot of jitter to the clock signal. There don't seem to be any dedicated IC for this purpose which makes me think it is as simple as using a LVDS driver and terminating one of the inputs. Am I on the right path here?

Thank you very much for your help and experience!

Thomas
 

Offline ejeffrey

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Re: CMOS logic OCXO to LVDS converter without adding too much jitter
« Reply #1 on: August 26, 2019, 03:42:26 pm »
TI has a whole family of LVDS <-> single ended logic transceivers, such as the DS90LV027A.  I'm not sure how their jitter compares to your OCXO. 

If you need really low jitter a high speed comparator with LVDS output will probably work better.  The LTC6957-2 is a high speed LVDS driver that is mostly intended to be used as a low jitter clock sine->square converter.  It is probably overkill for your application.
 

Online David Hess

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Re: CMOS logic OCXO to LVDS converter without adding too much jitter
« Reply #2 on: August 26, 2019, 04:21:35 pm »
If your LVDS driver has differential logic inputs then terminating one input to control duty cycle is exactly what to do.  The differential inputs allow common mode noise in the ground and power connections to be rejected unlike with single ended logic.  This implies being careful about ground loops between the single ended output from the oscillator and the conversion logic which is what differential inputs allow.

If I could not take advantage of differential inputs on the LVDS converter, then I would use a single point ground to the oscillator and carefully regulate the common supply voltage to the oscillator and LVDS converter.  It may be sufficient to LCR decouple the power supply to remove high frequency noise but supply voltage drift will cause jitter over long time periods.
 


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