how to calculate PLL spur both integer and fractional ?

[eeliuliu]

pll spur

hi, eveyone,
I'm trying to calculate PLL spur both integer N and fractional N. Could you please give some advice ? Thank you very much!

 

[yellff]

pll frac spurious

Do you means the phase noise ?

 

[eeliuliu]

calculate pll

Do you means the phase noise ?

not phase noise, it's spurious level

 

[hanjiemy]

first, u must calc the spurious frequency for integer and frac. then u must calc the spuriou gain, every spurs from diff block have diff transfer factor. Finally, simulate it... In fact, we don't calc it usually. we just have good design in charge pump design, such as mismatch, leakage, timing. You must consider the power/gnd line coupling, ESD coupling and sub leakage, and the spur level is really not easy to pre-calc, but you can get the approximation by smart way.