Patent ID: 7307568
Filing Date: 2007-12-11
Classification: H03M

Abstract:
1. A method to eliminate inter-symbol interference error at an I-to-V output stage of a current steering DAC having a plurality of current cells, said output stage comprising at least an I-to-V amplifier having summing junctions SJP and SJN, feedback resistances R 1 and R 2 , and feedback capacitances C 1 and C 2 , said method comprising the steps of: disconnecting said feedback resistors R connecting said feedback resistors R using the I-to-V amplifier as a buffer to maintain a CM level at drains of said current cells during said hold period by connecting the outputs of said current cells to midpoint of said resistor string; and changing DAC codes while outputs of said current cells are in said hold mode, and disconnecting the outputs of said current cells from each other after the DAC codes are changed and re-connecting said feedback resistors and appropriate outputs of said current cells back to the summing junctions of said I-to-V converter.