Dear expert,
My system is UB962 with UB935.
Among 5 boards, there are 2 boards randomly fail to LOCK occasionally even after 1500ms waiting time.
For good bards, UB962 0x4E register is 0x4. For bad boards, 0x4E register is 0xA which indicates Frequency measurement is not stable.
Then I remove external clock to force UB962 run with internal reference clock. The problem is gone.
All of phenomenon indicates external clock problem. However, external clock reference measurement is very stable as below picture.
The problem is reproducible. Re-soldering silicon cannot make problem gone.
