| This paper discussed the DC convergence problem during SPICE circuit simulation through analyzing the illness of various real designs which may cause the DC non-convergence problem, comparing the current different modified DC convergence algorithms and pointing out the advantages & disadvantages for each algorithm. Based on these analysis, the author comes up with one new algorithm for helping to improve the DC convergence named: two-dimension G-G ramping method, which is based on N-R iteration method, includes the "Gmin" stepping method as one dimension, new "Gshunt" ramping method added as the other dimension to help NR iteration to converge to the right value. When both of the two dimension parameters are stepped to enough small value and solution satisfied with the right convergence tolerance, then it lets program get the final DC solution. Because implementing this algorithm in some commercial SPICE software successfully, it is proved as one practical algorithm to help the tool to improve the DC convergence ability for real customer designs. |
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