We are using AD9548 in our design and we are experiencing phase noise issues on its output. Below are the details of the AD9548 configuration.
Sysclock: 12.8MHz, OCXO (attach is the phase noise plot of the OCXO vs 40MHz output)
Internal System clock: 998.2MHz
DAC out: 200MHz
AD9548 Mode: Freerun
Output frequency: 40MHz (attach is the phase noise plot of the OCXO vs 40MHz output)
reference clk in: powered down.
unused output: powered down.
1. I assume the best phase noise that we can get when we are on free run mode is close to the system clock phase noise. Is this assumption correct? I attached the phase noise plot of the system clock 12.8MHz and the 40MHz output and looks like I am seeing spur and high phase noise issue @ free run mode.
2. I attached our AD9548 configuration (*.stp), can you please take a look at the configuration and let me know if you see issues contributing to the observation above?