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https://designersguide.org/forum/YaBB.pl Analog Verification >> Analog Functional Verification >> why bode plot of a linear pll model got from spectre is different from simulink? https://designersguide.org/forum/YaBB.pl?num=1484895791 Message started by lwzunique on Jan 19^{th}, 2017, 11:03pm 
Title: why bode plot of a linear pll model got from spectre is different from simulink? Post by lwzunique on Jan 19^{th}, 2017, 11:03pm I tried to build pll linear model in cadence spectre. but when i do ac simulation, I found that the magnitude of the bode response plot is different from that I got from matlab simulink model, why there is this diference? in the figure below, the bode plot of these three model are the same. and the veriloga model is: Code:

Title: Re: why bode plot of a linear pll model got from spectre is different from simulink? Post by lwzunique on Jan 19^{th}, 2017, 11:11pm matlab simulink simulation result: kpfd=124uA/(2*pi) Kvco=40M/v divider ratio N=115 R1=33K R3=36K C1=161p C2=C3=2pF these values are the same in spectre and simulink. as we can see the loop bandwidth is very similar, and the phase margin is also almost the same. why the magnitude is so different? in spectre simulation the magnitude at the beginning is about 200dB, but in simulink is about 60dB. 
Title: Re: why bode plot of a linear pll model got from spectre is different from simulink? Post by lwzunique on Jan 19^{th}, 2017, 11:23pm really sorry for my mistake, I know why, the beginning of the frequency is not the same. 
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