ADS5403: LVPECL / LVDS oscillator design

Richard,

There might be a chance your clock amplitude is to low. Verify the clock input amplitude is within the specs shown in Figure 25 of the data sheet. Common mode should not be an issue since you are AC coupling. Double check the termination required by the oscillator. The LVPECL devices we use only require a 240 Ohm resistor to GND on each output leg.

Regards,

Jim  

Jim thanks a lot for answering,

  We are using this part https://www.mouser.com/datasheet/2/3/AX5-1509995.pdf  and following the datasheet recommendations for LVPECL. It is quite possible that this part is incompatible with the ADC. I have a fundamental lack of understanding regards the 240 ohm to ground, It seems at odds with your internal biasing scheme and also the characteristic impedance of the board.

I'll take your advice though, could I ask you to send me the exact oscillator part number and biasing arrangement, I'll use it.  

Thank a lot Rob, 

 I didn't realize you were an artist! do you care if the LVPECL is 2.5V rather than 1.8V? . The oscillator that we currently use is not available in 1.8V LVPECL. It shouldn't matter given that it is AC coupled right?

I appreciate all of your help.