Patent ID: 7671775
Filing Date: 2010-03-02
Classification: G09G,H03M

Abstract:
1. A converter for converting an N-bit digital signal (N is an integer of three or more) into an analog signal using a plurality of different reference voltages, comprising: a selection voltage divider circuit having a plurality of MOS transistors each functioning as a switch, wherein the selection voltage divider circuit selects two of the plurality of reference voltages via respective sets of MOS transistors of the plurality of MOS transistors, the sets having the same number of MOS transistors, in accordance with the (N−m) most significant bits of the digital signal, and divides a difference between the two selected reference voltages into M by combined ON-resistances of M MOS transistor groups connected in series of the plurality of MOS transistors to obtain (M−1) intermediate voltages, where m is an integer of one or more and M is an integer of 2 a mode selection circuit for determining a magnitude of the combined ON-resistance of each of the M MOS transistor groups of the selection voltage divider circuit, selecting a first mode when the combined ON-resistance is large and a second mode when the combined ON-resistance is small, and performing a control so that the number of MOS transistors included in each of the M MOS transistor groups in the selection voltage divider circuit is larger in the second mode than in the first mode; and an output circuit for selectively outputting one of the two selected reference voltages or one of the (M−1) intermediate voltages as the analog signal in accordance with the m least significant bits of the digital signal.