Noise coupling analysis of power distribution network and signal traces in high-speed system on package (SoP)

Abstract

In today’s digital systems, on-chip and off-chip (chip-to-local) clock frequencies are increasing rapidly and are expected to exceed 10 GHz by 2010. In addition, the supply voltage is scaled down to less than 1 V, and the power dissipation increased to hundreds of watts. These technology trends result in significant simultaneous switching noise (SSN), which is proportional to the switching current magnitude and operating frequency. The noise is primarily generated by high-speed digital processors and is coupled through the power distribution network (PDN), resulting in significant jitter for phase-locked loops (PLL) and phase noise for the RF oscillator, resulting in reduction in the timing margin and the noise margin, and in degradation of the bit error rate (BER). The noise in a PDN is likely to be increasingly coupled to signal traces as the layout density of the digital circuits increases in highly integrated multilayer structures of packages and printed circuit boards (PCBs). Many signal traces may be routed, including layer transitions through vias, and some power/ground planes are partitioned into several island planes in highly integrated systems. Simultaneously, the increasing speed of the signal requires tighter noise margins and stricter signal integrity. Therefore, the coupling of the power/ground noise to signal traces causes problems for signal quality and timing and ultimately degrades the high-speed performance. It has been demonstrated that SSN induced by a digital chip mounted on a multilayer PCB is closely coupled to nearby signal traces, and the characteristics of the noise coupling depend on the operating frequency. Therefore, a precise modeling technique to describe the coupling phenomenon is becoming necessary. To date, in most studies, the whole structure, including both the PDN and signal trace, has been considered to determine how strongly the switching noise is coupled to the signal trace. If factors and mechanisms associated with...