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Chapter 20<br />

Speed and Accuracy<br />

Eldo provides different algorithms and control options, which are used to balance speed with<br />

accuracy. Most of the information in this chapter relates to transient analysis, as it is the most<br />

time-consuming analysis, and also the most frequently used analysis.<br />

Introduction to Speed and Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1243<br />

Speed and Accuracy in Eldo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1245<br />

Integration Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1246<br />

Time Step Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1248<br />

Newton Iterations Accuracy Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1252<br />

Global Tuning of the Accuracy—EPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1253<br />

Global Tuning of the Accuracy—TUNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1255<br />

Simulation of Large Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1256<br />

Tips for Improving Simulation Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1259<br />

Integral Equation Method (IEM) Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260<br />

IEM Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1261<br />

IEM—Supported Circuit Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1262<br />

IEM Tolerance Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263<br />

Efficient Usage of IEM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1264<br />

One Step Relaxation (OSR) Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1265<br />

Introduction to Speed and Accuracy<br />

The trade-off between speed and accuracy is the primary concern of <strong>user</strong>s designing<br />

simulations. Circuit-level transient simulation is the numerical resolution of an algebraic<br />

differential system of equations; as such, it is not an exact procedure (unlike the linear AC or<br />

NOISE analyses), and many switches can be used to control the accuracy of the results.<br />

Typically, improved accuracy comes with an increased CPU time.<br />

Eldo includes three different algorithms: NR (Newton-Raphson), OSR (One Step Relaxation),<br />

and IEM (Integral Equation Method). The majority of information in this chapter is dedicated to<br />

speed and accuracy with the default Newton-Raphson algorithm.<br />

Caution<br />

OSR and IEM are legacy algorithms, there are no active developments, enhancements, nor<br />

bug fixing. To simulate with a higher performance than Eldo Classic, consider Eldo<br />

Premier.<br />

Eldo® User's Manual, 15.3 1243

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