charge pump related loop simulation in PLL

Started by fl July 2, 2018
Hello all:
Though my question is not in the strict DSP, I cannot find another appropriate
forum to discuss about it. As a hobby, I am interested in a PLL simulation.
On numerous tutorials, I know there are current sources in a charge pump type
phase detector. I realize that the current source makes the voltage cross
the capacitor linearly increase. It is seen the Laplace transform of the RC 
network connecting to the charge pump. My question is "how do I simulate this
current source driven RC network"?
I've noticed that a difference between a current source and a voltage source,
but I don't see:
1. What analysis difference between the same RC network for these two sources?
I know Laplace is a tool for analog circuit analysis, but I am not clear on
how to use it in a current source signal analysis
2. In a Matlab/Simulink simulation, how to simulate a current source input?
I do see a current source library component, but it is from "Electrical Sources"
lib. I don't know how to use it with a Laplace transfer function.

I've been familiar with DSP, but feel quite new on analog circuit analisys.


Thanks a lot
On Monday, July 2, 2018 at 5:06:42 PM UTC+12, fl wrote:
> Hello all: > Though my question is not in the strict DSP, I cannot find another appropriate > forum to discuss about it. As a hobby, I am interested in a PLL simulation. > On numerous tutorials, I know there are current sources in a charge pump type > phase detector. I realize that the current source makes the voltage cross > the capacitor linearly increase. It is seen the Laplace transform of the RC > network connecting to the charge pump. My question is "how do I simulate this > current source driven RC network"? > I've noticed that a difference between a current source and a voltage source, > but I don't see: > 1. What analysis difference between the same RC network for these two sources? > I know Laplace is a tool for analog circuit analysis, but I am not clear on > how to use it in a current source signal analysis > 2. In a Matlab/Simulink simulation, how to simulate a current source input? > I do see a current source library component, but it is from "Electrical Sources"
lib. I don't know how to use it with a Laplace transfer function.
> > I've been familiar with DSP, but feel quite new on analog circuit analisys. > > > Thanks a lot
Once you have a transfer function in terms of Laplace(assuming it is linear), use the Bilinear transform to convert it to a z-transfer function, then implement the difference equation.
W dniu poniedziałek, 2 lipca 2018 18:49:55 UTC+1 użytkownik
gyans...@gmail.com napisał:
> On Monday, July 2, 2018 at 5:06:42 PM UTC+12, fl wrote: > > Hello all: > > Though my question is not in the strict DSP, I cannot find another appropriate > > forum to discuss about it. As a hobby, I am interested in a PLL simulation. > > On numerous tutorials, I know there are current sources in a charge pump type > > phase detector. I realize that the current source makes the voltage cross > > the capacitor linearly increase. It is seen the Laplace transform of the RC > > network connecting to the charge pump. My question is "how do I simulate this > > current source driven RC network"? > > I've noticed that a difference between a current source and a voltage source, > > but I don't see: > > 1. What analysis difference between the same RC network for these two sources? > > I know Laplace is a tool for analog circuit analysis, but I am not clear on > > how to use it in a current source signal analysis > > 2. In a Matlab/Simulink simulation, how to simulate a current source input? > > I do see a current source library component, but it is from "Electrical Sources"
lib. I don't know how to use it with a Laplace transfer function.
> > > > I've been familiar with DSP, but feel quite new on analog circuit analisys. > > > > > > Thanks a lot > > Once you have a transfer function in terms of Laplace(assuming it is linear), use
the Bilinear transform to convert it to a z-transfer function, then implement the difference equation. For a nice practical example of that method suggest to visit http://www.aholme.co.uk/Frac2/Simulate.htm Kind regards, Adam