New over-range protection scheme in pipelined data converters

Existing approaches for the design of inter-stage switched-capacitor amplifiers used in pipelined data converters have evolved following the notion that there are firm limits on input range and output range of the amplifier. In this work, it is recognized that the limits on signal swing are not dictated by binary and somewhat arbitrary boundaries but rather by increasing levels of distortion with signal swing. The concept of defining a series of signal swing windows based on the degree of distortion present in the gain stage amplifier is formalized. A set of "critical points" on the transfer characteristics are identified that are useful for determining robustness of any given over-range protection circuit. In contrast to existing approaches where the amplifier may be under-designed or over-designed in an attempt to meet a fixed signal swing window requirement, the designer can select signal swing windows to provide acceptable levels of distortion. Following this approach, a new over-range protection scheme is developed which ensures that all residues of a given stage are mapped back into an acceptable distortion window of the following stage