Worst Case Power/Ground Noise Estimation Using an Equivalent Transition Time for Resonance.

The nonmonotonic behavior of power/ground noise with respect to the transition time t_r is investigated for an inductive power distribution network with a decoupling capacitor. The worst case power/ground noise obtained with fast switching characteristics is shown to be significantly inaccurate. An equivalent transition time that corresponds to resonance is presented to accurately estimate the worst case power/ground noise in the time domain. Furthermore, the sensitivity of the ground noise to the decoupling capacitance C_d and parasitic inductance L_g is evaluated as a function of the transition time. Increasing the decoupling capacitance is shown to efficiently reduce the noise for transition times smaller than twice the LC time constant, t_r ⩽ 2 √L_gC_d. Alternatively, reducing the parasitic inductance L_g is shown to be effective for transition times greater than twice the LC time constant, t_r ⩾ 2 √L_gC_d. The peak noise occurs when the transition time is approximately equal to twice the LC time constant, t_r ≈ 2 √L_gC_d, referred to as the equivalent transition time for resonance. [ABSTRACT FROM AUTHOR]