Packaging Tradeoff for SIP Integration Targeting High Speed PAM-4 Applications
High speed transmission systems using optical fiber are now focusing on 4-level PAM (Pulse Amplitude Modulation) format. This is requesting ultra-wideband electronic system in package, with a high phase linearity behavior in order to drive the electro-optical modulators. Moreover, new power DAC (Digital to Analog Converter) dies, are now available to generate up to 56 GBd, 4-level PAM signals, and providing 4Vpp of differential output amplitude swing. High frequency studies have been pursued to provide system integration in a BGA (Ball Grid Array) package. The BGA package transitions optimization and the configuration of multi-lines carriers, becomes a key step in the design flow. In this paper, some steps of the design, manufacturing process of the SIP (System In Package) and its demonstration board are proposed. The choices of the package, the thermal management, the clock management function are studied according to the final environmental constraint of the SIP. The data lines phase skew are analyzed with the support of EM (Electro Magnetic) simulations to better understand the potential impact on the output eye. Finally, the BGA package transition, simulated and measured results are compared, from DC up to 40 GHz and the measured SIP output, 4 levels, 56GBps eye diagram is presented.