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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> uncertain settling time with analog artist https://designers-guide.org/forum/YaBB.pl?num=1133490906 Message started by nus_lin on Dec 1st, 2005, 6:35pm |
Title: uncertain settling time with analog artist Post by nus_lin on Dec 1st, 2005, 6:35pm I found that the setup of transient analysis is tricky for the simulation of settling time. the settling time extracted is strongly dependent on the setup, say, for the default setup, the 0.1% settling time is 28ns, but if i manually set the maxstep to be 5ps, the settling time became 36.6ns, if i change other setup such as soving method, the value also change. now my question is, which value is correct, which kind of setup has the best accuracy in terms of settling time extraction? |
Title: Re: uncertain settling time with analog artist Post by Sezi on Dec 2nd, 2005, 3:38am The settling time depends on the simulation step: the smaller the simulation step, the higher the accuracy. In real life, the simulation step corresponds to infinitely small time duration so I think if you set the simulation step smaller, your result will be more accurate, but will take longer time to simulate. |
Title: Re: uncertain settling time with analog artist Post by sheldon on Dec 2nd, 2005, 3:58am nus_lin, It would help if you provided more information, for example, the log file. The amount of variation in the settling time that you are describing seems rather large. How stable is the amplifier, is it ringing as it settles? Is the simulation just the settling time of an amplifier or ar other things events occuring in the simulation? Are there any special devices in the simulation, for example, an n-port? Also would it be possible to list up the simulation conditions that you tried and the results? Best Regards, Sheldon |
Title: Re: uncertain settling time with analog artist Post by vivkr on Dec 3rd, 2005, 12:19am Hi nus_lin, The choice of the integration method and the accuracy setting have a significant impact on the calculation of the settling time or other transient timeconstants. Ideally, the trapezoidal integration method is the best as it is lossless, and will also show you any potential overshoot and ringing. However, there is no reason why the gear2 method will not work effectively provided your accuracy settings are tight enough. How tight they ought to be is something which depends on the target accuracy of the circuit you are simulating. Please look up the chapter on Transient Analysis in the book "The Designer's Guide to SPICE and Spectre" by Ken Kundert for more details. Regards Vivek |
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