Patent ID: 6747626
Filing Date: 2004-06-08
Classification: G09G

Abstract:
A dual mode source driver circuit for driving an LCD panel having reference voltages having low power consumption, comprising:a shift register having a plurality of N addressable channels; a plurality of data inputs connected to the source driver circuit for receiving input data indicative of an image to be displayed on the LCD, the input data being at a first digital input voltage level; a plurality of sample registers coupled to the shift register, each sample register coupled to a corresponding one of the plurality of data inputs to receive the input data; a plurality of hold registers, each hold register coupled to a corresponding one of the plurality of sample registers to receive the sampled input data, the plurality of hold registers coupled to receive a transfer signal wherein the transfer signal determines the timing for the transfer of sampled input data from each sample register to each respective hold register; an internal resistive digital to analog circuit to produce linear voltage levels between any pair of adjacent reference voltages; a plurality of decoder cells, each decoder cell coupled to the internal resistive digital to analog circuit and each respective hold register such that each decoder cell is programmable to decode the input data to select respective output voltage levels; a plurality of output cells coupled to receive a mode signal to activate each output cell, each output cell coupled to receive the held input data from each respective hold register, wherein each of the plurality of output cells comprises, an inverter coupled to receive the input data, an AND gate coupled to the inverter and coupled to receive the mode signal, an NAND gate coupled to receive the input data and the mode signal, a P-type transistor, having a drain, a source, and a gate, the gate coupled to the NAND gate, the source coupled to a high voltage supply, the drain coupled to the output of the output cell, and a n-type transistor, having a drain, a source, and a gate, the gate coupled to the AND gate, the source coupled to a low voltage supply, the drain coupled to the output of the output cell; a plurality of switches coupled to receive a mode signal to activate each switch, each switch connected to each of the decoder cells for switching between a gray scale mode, having full color display resolution, and a standby mode of operation that decreases the amount of power dissipated and having a voltage output for the LCD sufficient to provide text, icon, graphic and video data, wherein, in the first mode, when each switch is closed, the output cells are bypassed and, in the second mode, when each switch is open, the decoder cells are bypassed; and a plurality of driver outputs coupled to the plurality of output cells and the plurality of switches to receive each respective output voltage level for providing drive voltages derived from said input data to the LCD panel.