- Operating frequency: 3 GHz
- Ref frequency: 20 MHz
- Charge Pump: High Current mode
- Integer-N Mode
PLL locks at first, then gradually spectrum spreads out only in higher frequency direction and goes out of lock.
- Ref divider output is good
- N divider output is quite low
- Charge pump is railed low
- VCO is sourcing current!
We have two boards exhibiting this behavior, each boards has 2x ADF5355 chips installed. Replaced the chips --- observed the same issue.
Attached are circuit diagram and programming code.