A binary-to-thermometer decoder with built-in redundancy for improved DAC yield

This paper describes an architecture for binary-to-thermometer decoders used in segmented D/A converters. To improve basic converter characteristics, the architecture features redundant output thermometer code. The main concept offers two modes of operation. Each mode generates a different thermometer output, i.e. a different switching sequence for the DAC MSB thermometer analog elements. This results in two different transfer characteristics of the whole DAC for the same mismatch errors of its elements. After on-chip or off-chip measurements, the more linear transfer characteristic can be selected. In this way, chip yield is improved and the design requirements can be relaxed. Ultimately, the advantages introduced by the proposed decoder lead to cheaper and smaller D/A converters