CDCE62005 lock problem, recalibration unreliable

Ali,

With this type of problem there are three common factors affecting the devices ability to get a stable lock: loop filter configuration, input settings, and calibration.

I loaded up one of our EVMs with your settings and the device locked. Your register settings look OK, and your loop filter configuration looks good.

I believe that what is probably the case is the calibration. Calibration happens automatically when the settings are loaded from the EEPROM. However, when loading the settings with an SPI interface, you must also manually re-calibrate the device. You can do this by clicking on the "Calibrate" button in the GUI.

I loaded your device settings using the GUI without writing them to the EEPROM. The device did not lock until I initiated the manual calibration. After writing your settings to EEPROM and cycling power, the device comes up and locks right away. Can you confirm that the same happens on your end?

If not then the problem could be with the input signaling type. I am assuming from your register settings that you are using an LVPECL input signaling type on the primary input. Please confirm that this is the case, and also make sure to check your signaling voltage levels.

I hope this helps, Please let me know if you have any more problems and we can debug further. Thanks!

Regards,

Brandon Vonk

Hi Brandon,

We seem to have an issue with manual recalibration, it sometimes causes chip to lock, sometimes it does not (and I can tell it calibrated because the calibration value - reg8 5:0 - seems to have changed). I saw on another post how writing the wrong value to reserved bits might prevent recalibration and went over our settings. There were many reserved bits that should not have been set, and a few that should have been set. After correcting these manual recalibration seems to work.  The GUI does not seem to care about these reserved bits, it would be nice to have some kind of a warning or restriction that it would not generate register settings with these reserved bits sets illegally.

I will continue testing these new values to see if the problem is actually solved. Will update.

Thanks!