Low Output Offset, 8-bit Signal Driver ICs for XGA/SVGA TFT-LCDs

Abstract

Two types of low output offset 8-bit signal driver ICs for XGA/SVGA TFT-LCDs are described. These driver ICs generate 256 gray-scale levels using 11 reference voltages. One type incorporates a DAC using a capacitor array (C-DAC) and the other a DAC using a resistive divider(R-DAC). Using a fast offset-cancel circuit, the output-offset voltage of each driver has been reduced to within ±5mV (1/2 LSB) with the settling time of 10μsec for 150pF load capacitance. These driver ICs can operate at up to 55MHz at 3.3V. Both driver ICs have 309/300 outputs. They were fabricated using standard 0.6μm CMOS technology for logic ICs. The die areas of the drivers are 38.9mm² for the C-DAC, type and 47.6mm² for the R-DAC type; it is found that the C-DAC type is more cost-effective than the R-DAC type.