Overshoot control for two coupled RLC interconnections

An algorithm is introduced to upgrade package performance for two coupled lines. A compromise between fast response and limited undershoot is based upon a 4% overshoot control condition. It is easy to use this time domain requirement because it can be applied to the transfer function in the frequency domain. In the frequency domain, it is known that a low-frequency approximation to the transfer function provides a simple and accurate trade-off requirement for single-mode overshoot control. For mixed mode, i.e. for the case of one driven line and one quiet line, it is shown here that the same approximation can be used to control the overshoot in the weak coupling case. A closed-form relationship among electrical line and termination parameters results. However, for strong coupling (small line spacing), the time domain transient response with parameters based on the closed-form relationship is inaccurate. For strong coupling it is shown here an average-transfer-function (ATF) method can be used for calculating trade-offs when multiple modes are excited.<
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