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EV-ADF4355SD1Z single ended clock usage

Question asked by ericc_engineer on May 25, 2018

I have two use cases I want to try.  One where I'm using a 10MHz reference input, the other a 400MHz input.  I can get it to work by Removing R12. But I just don't understand what the user guide is trying to tell me.

 

To use a single-ended REFINx, connect a low noise 122.88 MHz reference source to SMA REFINB, and connect a 50 Ω terminator to SMA REFINA. Remove Resistor R27 (100 Ω). To use a differential REFINx, connect the differential signal to SMA REFINA and SMA REFINB.

 

  • Why would I have to connect a 122.88MHz reference to REFINB if I just want to use a single ended input on REFINA?  Can't I just GND it or float it?
  • I assume the 50 Ohm terminator on REFINA is to GND right?
  • The datasheet for the ADF4355-2 says maximum single ended input frequency is 250MHz.  It seems to run just fine when I put in a 400MHz single ended input on REFINA.  What are the consequences of doing this?  

 

Thank you

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