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https://designers-guide.org/forum/YaBB.pl Design Languages >> Verilog-AMS >> How to creat a loop filter model in VerilogA https://designers-guide.org/forum/YaBB.pl?num=1156211332 Message started by semitao on Aug 21st, 2006, 6:48pm |
Title: How to creat a loop filter model in VerilogA Post by semitao on Aug 21st, 2006, 6:48pm Hi, I want to creat a loop filter model in VerilogA. I found most loop filter model use R and C component, but I try to use the laplace function to describe this model, is that feasible? |
Title: Re: How to creat a loop filter model in VerilogA Post by ACWWong on Aug 22nd, 2006, 4:02am yes, laplace function should work fine... i think there used to be a "hidden state" problem with it in spectreRF simulations, but this has gone away now... |
Title: Re: How to creat a loop filter model in VerilogA Post by jbdavid on Aug 29th, 2006, 11:25am One of the problems I had with La-place is the fact that is immutable once setup.. IE you Can't change the transfer function during the transient simulation.. which is a problem if you can switch capacitance or resistance in or out of the circuit to adjust for process, thermal, variation, or to handle different types of inputs... maybe not generally the case for PLL loop filters, but thats not the only place where this might be used. I once developed 32 parallel laplace functions and picked the one selected by the control signal (a bus) but today I'd use a differntial model and change the coefficients based on the control signals.. ie Code:
of course you might want to change the capacitance nicely (transition) and get I(cap) to behave correctly on the transition, but you get the idea.. Jbd |
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