a digital - to - analog converter includes a first input end for reversely receiving a digital signal , a second input end for receiving multiple reference voltages arranged in a best order , wherein the best order is determined by reordering an initial order several times , multiple first switches coupled to each other stage by stage like a tree for selecting one of the reference voltages to be a first selection result , multiple second switches coupled in series for selecting one of the reference voltages to be a second selection result .