In-depth study of simultaneous switching noise patterns for different signaling topologies

Simultaneous switching noise (SSN) is one of the key performance bottlenecks in design of single-ended signaling systems such as DDRx, LPDDRx, and LVTTL interfaces. Good power distribution network (PDN) is a must for high-end system designs. Due to design limitation in die and package, providing sufficient on-die capacitor (ODC) or on-package capacitor (OPD) is a very challenging task. In this paper, we propose a novel on-die decoupling scheme which places decoupling caps in core area and connects to I/O area by package interconnects. Single-ended signaling is also a common choice for SiP interface designs including WideIO interface where SSN impact can dominate the timing error compared to on-board interface designs where crosstalk is still the most critical factor for timing error. One of the crucial tasks in SSN analysis is determining the excitation data pattern. We also propose a reasonable worst case SSN data patterns for both terminated and un-terminated channel types and compare the performance using simulations.