Digital-to-analog converter having efficient switch configuration

Abstract

A DAC includes a gamma voltage generator for generating a plurality of gamma voltages, and a decoder for receiving an M-bit digital value for selecting one of the gamma voltages, wherein the decoder comprises a first thermometer encoder, a first selector and a second selector. The first thermometer encoder is utilized to receive N bits of the digital value to generate a first thermometer code with 2N bits, wherein N is smaller than M, and M and N are positive integers. The first selector has a plurality of selecting groups, each selecting group having 2N switches controlled by the first thermometer code to output one gamma voltage, where the second selector receives the gamma voltages outputted by the selecting groups of the first selector and outputs one gamma voltage selected from the received gamma voltages based on the (M−N) bit of the digital value.

Description

BACKGROUND OF THE INVENTION [0001]1. Field of the Invention[0002]The present invention relates to a digital-to-analog converter (DAC) configuration, and more particularly, to a DAC that uses fewer switches and has a more efficient circuit configuration.[0003]2. Description of the Prior Art[0004]As shown in FIG. 1, a conventional DAC 100 is formed by a resistor string 110 and a plurality of binary selectors 120. The resistor string 110 is electrically connected between a first voltage level V1 and a second voltage level V2 so that each terminal of the resistors in the string 110 has a specific and different voltage level. Each binary selector 120 includes two switches 122 and 124 respectively controlled by a binary bit and its inverse. The switch that corresponds to the bit having a value equal to ‘1’ will be switched on, while another switch that corresponds to the bit having a value equal to ‘0’ will be switched off. Please refer to FIG. 2, which shows an example illustrating how t...

AI Technical Summary

Benefits of technology

[0006]One objective of the present invention is therefore to provide a DAC that uses fewer switches and has more efficient circuit configuration. When the DAC is implemented in a source driver of a liquid crystal display (LCD) device, the gamma coupling and power consumption can both be reduced.

Problems solved by technology

As the bit number of the digital value increases, the number of switches required grows significantly, resulting in increases of chip area and power consumption for the DAC.

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