A study of dynamic element-matching techniques for 3-level unit elements

Highly linear 3-level unit elements are available in any fully differential circuit. This is because each unit element in such a circuit can be either positively selected, negatively selected, or not selected. This paper presents a study of dynamic element techniques for such elements. It is shown how traditional dynamic element-matching techniques for 2-level unit elements such as the data directed swapper, the vector selector and the tree structure can be adapted toward linear 3-level elements. In all these cases, the amount of hardware is reduced significantly by using 3-level elements. Also several efficient "data weighted averaging"-like implementations are presented. Then the effect of the nonlinearity of the 3-level unit element is analyzed. It is shown that this gives an additional error contribution that may limit the performance. Therefore, several efficient techniques to shape this effect as well are introduced.