PSpice Application Notes

PSpice - Transmission_line_Applications_in_PSpice

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6 Figure 4. Near and far end crosstalk resulting from a step input on an adjacent line "Long " vs. "Short" Lines Defining the point at which an interconnect should be treated as a transmission line and hence reflection analysis applied has no consensus of opinion. A rule of thumb is when the delay from one end to the other is greater than risetime/2, the line is considered electrically long. If the delay is less than risetime/2, the line is electrically short. Hence, the following guidelines: Lumped line: tr/Td >=4 Short line: 4 > tr/Td > 2 Long line: tr/Td <= 2 "Lumped" and "short" lines may always be modeled by lumped circuits. The topic of the next section is to decide how to best model an electrically "long" line.

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