Statistical Analysis of Simultaneous Switching Output (SSO) Impacts on Steady State Output Responses and Signal Integrity

Abstract

Due to technical trends requiring high memory bandwidth, the number of output buffers is increasing which generates non-linear power/ground noise associated with simultaneous switching output (SSO). However, the SSO also causes fluctuation in output responses of buffers remaining in steady states. In this paper, for the first time, impacts of SSO buffers on steady state output responses and signal integrity of high-speed channel are analyzed based on statistical method. Output step responses not only for pull-up/down transitions but also steady states affected by SSO are obtained using transient simulator. Then, occurrence probability of each SSO combination is mapped to corresponding output response to generate output response probability density functions (PDFs). Using the derived PDFs statistical eye-diagrams are derived to validate the impacts of SSO on overall shape of the eye-diagram. Finally, the proposed method is compared with conventional statistical method.