Reflection analysis of signal transmission in 32-bit CPU based SiP

Signal integrity is an important issue in SiP (System in Package) which has complex interconnection and communication among chips in one package. The researches concerning both reflection and crosstalk are of great significance. This paper focuses on the study of restraining reflection of one transmission line which is the fundamental element of signal quality. The simulation and analysis are based on a SiP which packages four components together, including a 32-bit CPU (Loongson 1B) and three memories (one Flash and two EEPROMs). Through analysis and comparison, a best method of impedance matching to restrain reflection is designed which reduces overshoot by 98.68% and reduces undershoot by 79.26%, compared with the situation without impedance matching.