Effect of mutual coupling between signal traces and ground planes on SSO noise in packages with multiple stacked ground planes

The mutual coupling between signal traces and ground planes in packages with multiple, stacked ground planes, and its effect on the value of the effective inductance for simultaneous switching output (SSO) noise is discussed. Based on the idea of an effective width for the current path under the signal trace in the ground plane, two models for the ground plane inductance are proposed at low and high frequency, respectively. SPICE simulation results for SSO noise are shown using the proposed models, which show that additional planes will help in reducing the value of the effective inductance of the ground path, and hence reducing the value of SSO noise.