xihuwang
Member level 2
pllpuzzler
A problem on pll puzzle me :
Look at the below 2 figs
fout = (N/R)*fin in fig 1 and fout = (N/(P*R))*fin
and
N,R,P is equal to 1, 2 ,3 ,....16
My question is :
When N varies, for example from 1 to 16, the loop gain
will change 16 times . To keep bandwidth and ξ constant,
current of charge pump or the R and C in LPF have to
be adjusted, which is difficult for my design.
If I keep N constant and equal to 16, then the loop
parameters will not vary . But I found the frequency
divider P is difficult to design If I want the P can work
with the same speed as VCO and P has 50% duty cycle.
Added after 48 minutes:
Will anyone help me ?
A problem on pll puzzle me :
Look at the below 2 figs
fout = (N/R)*fin in fig 1 and fout = (N/(P*R))*fin
and
N,R,P is equal to 1, 2 ,3 ,....16
My question is :
When N varies, for example from 1 to 16, the loop gain
will change 16 times . To keep bandwidth and ξ constant,
current of charge pump or the R and C in LPF have to
be adjusted, which is difficult for my design.
If I keep N constant and equal to 16, then the loop
parameters will not vary . But I found the frequency
divider P is difficult to design If I want the P can work
with the same speed as VCO and P has 50% duty cycle.
Added after 48 minutes:
Will anyone help me ?
