Hello, TI!
I am currently using the PLLattinnum sim tool to predict the spurious behavior of LMX2594. Through this tool, we can know that there are the following types of spurious behavior:
1. fpd_ Pluse
2. fpd_ Leakage
3. IBS
4. Prim factorial
5. Sub freight
6. mash_ Linear
7. mash_ Nolinear
8. fvco% fpd
9. Fvco% osc
10. out% osc
Currently, I can predict most of my spikes through tools, but there are still a few spikes that I don't know how to calculate predictions,
For example:
Prim divergence, I can predict by calculating FPD% Fden using PLLaltinnum sim's prompt that these spurs are even or odd harmonics of this,
however
According to the prompts from PLLaltinnum sim, calculate FPD% Fden for the SUB farctional, but the simulated data does not correspond to the actual simulation data. Why?
Let me give an example. I want to obtain FOUT=4851.1, FPD=200MHZ, OSC=100MHZ,,Fden=1000 as shown in Figure 1
Figure 1
Through the tool prompt, I can know that Prim factorial=FVCO% Fden=9702.2% 1000=200khz.
The simulation result shows that Prim factorial is 200khz and its higher harmonics, which is correct.（ Figure 2）
Figure 2
Through the tool prompt, I can know that sub factor=FVCO% Fden=9702.2% 1000=200khz,.
However, the simulation result shows that the sub factorial is 100KHZ and its higher harmonics, which is inconsistent with the method calculated by the tool.（Figure 3）
Figure 3
I have tried other frequencies, and the results calculated by Prim factorial are consistent with the simulation results. However, the results calculated by sub factorial and the simulation results are not consistent. Please tell me the correct calculation method for sub factorial. I need to predict these spurs through calculation and then use other methods to eliminate or reduce them.
Best wishes.
