Higher order dynamic element matching by shortened tree-structure in delta-sigma modulators

The overall resolution of a multibit delta-sigma modulator is limited by its internal digital-to-analog converter (DAC) nonlinearity caused by mismatch errors. Recently, some dynamic element matching (DEM) methods were proposed to reduce mismatch errors, but they have serious problems of instability or hardware complexity. Between DEM algorithms, tree-structured scheme (TDEM) possesses some advantages in practical implementations but surfers more from instability in its algorithm. Based on TDEM, this paper presents a new shortened tree-structured algorithm. The proposed algorithm is sufficiently stable to handle second and third order mismatch shaping without any extra hardware over the conventional kind. Simulation results show a considerably improvement for mismatch shaping, stability and reducing its registers volume. Simulations are presented for a bandpass DSM. However, it can also be used in lowpass DSM.