Dynamic element matching (DEM) is often applied to multi-bit DACs to avoid nonlinear distortion that would otherwise result from inevitable mismatches among nominally identical circuit elements. Unfortunately, for such a… Click to show full abstract
Dynamic element matching (DEM) is often applied to multi-bit DACs to avoid nonlinear distortion that would otherwise result from inevitable mismatches among nominally identical circuit elements. Unfortunately, for such a DEM DAC to fully achieve this objective its constituent 1-bit DACs must be free of inter-symbol interference (ISI), i.e., the error from each 1-bit DAC must not depend on prior samples of the DAC's input sequence. This paper provides the first quantitative general analysis of the effects of ISI on the continuous-time outputs of DEM DACs. The analysis provides some surprising insights such as the conclusion that for certain types of DEM the only nonlinear distortion caused by ISI is second-order distortion. The paper also presents a digital pre-distortion technique that cancels the second-order distortion in the DEM DAC's first Nyquist band if information about the 1-bit DAC mismatches is available.
               
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