khsung
Newbie level 3
Let's assume that I am designing a fractional-N PLL.
2nd order MASH sigma-delta modulator is used.
The division ratio is selected as one of the four values(4,5,6, and 7) according to the output of the sigma-delta modulator output.
Let's assume that the effective division ratio is 5.3.
In the above case, when i calculate the phase margin,
Should i calculate the phase margin assuming N=5.3?
or
Should i calculate the phase margin assuming N=4,5,6, and 7 (four times) and then choose the worst phase margin?
whis is right?
2nd order MASH sigma-delta modulator is used.
The division ratio is selected as one of the four values(4,5,6, and 7) according to the output of the sigma-delta modulator output.
Let's assume that the effective division ratio is 5.3.
In the above case, when i calculate the phase margin,
Should i calculate the phase margin assuming N=5.3?
or
Should i calculate the phase margin assuming N=4,5,6, and 7 (four times) and then choose the worst phase margin?
whis is right?