Image UltrasoundX-ray OpticalIf the specifications are known from the application, the challenges in the design of A/D converters arise from the technology used.The application generally determines the integrated circuit (IC) technology, which is mainly a cost-driven choice.Due to the high level of integration of systems on a chip, the digital functionality and therefore the area occupied by digital circuitry becomes dominant.This means a technology has to be chosen that is optimized for digital circuitry.In this case the technology is optimized for high-density digital circuits, which allows the use of small feature sizes that achieve a high packing density.The parameters of this technology are typically optimized for the digital circuitry and are therefore less suitable for high-performance analog circuits.On the other hand, there are technologies that are better suited for the design of dedicated high-performance analog circuits.Although the stand-alone analog circuits can achieve a high performance, these components have to be integrated into the overall system at a higher, system-in-package (SiP) level.This is in contradiction with the increasingly higher level of integration of systems-on-a-chip (SoC).However, the use of multi-die packages as shown in figure 1.5 also offers advantages because the digital circuitry can be designed on a digital chip, in a dedicated digital complementary metal oxide semiconductor (CMOS) technology, whilst the analog circuits are designed in a dedicated analog technology.This allows fast scaling of the digital part whilst the analog performance with the analog chip is maintained and digital cross-talk is prevented.