Patent ID: 6157333
Filing Date: 2000-12-05
Classification: H03M

Abstract:
A method for selecting a sequence of cells including current sources inside a cell matrix bidimensional structure of a digital-analog converter wherein a variable number of current sources are switched on according to the value of an inputted digital signal and wherein a corresponding analog output signal is obtained by summing the respective outputs of the sources which are switched on, said bidimensional structure, considered as rectangular or preferably square, said bidimensional structure having first and second mean perpendiculars (M1, M2) and first and second diagonals (D1, D2), said bidimensional structure further including side to side and identical mapping areas for the cells, with each of said areas being attributed to a cell and with each cell including a same number of at least one current source, characterized in that it includes the following steps:a first step for selecting first and second areas (1,2) along a first diagonal (D1) of the structure respectively for a first and second cells on each side of a symmetry pint (S) located at a quarter of the diagonal length and away from the centre (C) of the rectangular or square structure and a pair of areas (3,4), respectively symmetrical of the first and second areas with regard to the centre (C) on the first diagonal, for a third and fourth cells,a second step for selecting four areas (5 to 8) symmetrical of the four areas selected by means of the preceding first step, with regard to the first mean perpendicular (M1), for the first, second, third and fourth cells,a third step for selecting a first of successive and yet unselected area (9,17,25) as a primary area (9), lined in a first area strip portion located between the said first area (1) and the other mean perpendicular (M2) of the rectangular structure, so that a further selection of a secondary area (10) is subsequently performed, said secondary area being symmetrical of this primary area (9) with regard to the symmetry point (S), so that a pair of areas (11,12) is selected as located symmetrical of these primary and secondary areas with regard to the centre (C), the primary area (9) neighboring the first area (1) being selected for the ninth cell, the corresponding secondary area (10) for the tenth cell and their respective symmetrical area (11, 12) with regard to centre (C) for the eleventh and twelfth cells,a fourth step for selecting four areas (13 to 16) symmetrical, from the four areas selected by means of the preceding third step, with regard to the first mean perpendicular (M1), for the ninth, tenth, eleventh and twelfth cells,a fifth step for repeating the third and fourth steps for successively each of the yet unselected areas located in the first area strip portion after the primary area(s) already selected, each time for eight successive cells,a sixth step for implementing the fifth step for each of the areas of a second area strip portion parallel to and neighbor of the first area strip portion in a zone limited by the said other mean perpendicular (M2) and a parallel (P1) passing through the symmetry point (S), in relation with a corresponding sequence of cells,a seventh step for repeating the sixth step, for each area strip portion, located in the zone and in parallel with the first area strip portion, with a side alternation from one area strip portion to the following one, and again in relation with a corresponding sequence of cells.