I have an AD9552 on my board that I was driving XTAL1 with a clipped sine wave oscillator (ac coupled with no biasing). REF was connected to VDD as described in the datasheet. The 9552 would lock, and the output appeared ok on my scope. However, now that I have the rest of my board fully assembled, I have gone back and found the 9552 is no longer locking. I want to ask if what I was doing was accepted behavior and not the cause of it no longer locking.