Accurate quadruple-gamma-curve correction for line inversion-based mobile TFT-LCD driver ICS

A line inversion-based gamma-curve correction scheme is presented for use in mobile TFT-LCD driver ICs. Novel voltage-symmetric gray curve synthesis (VSGS) method using a polarity-inverting gray voltage generator and variable resistor-tap biasing (VRTB) scheme using multioutput drivers have been adopted for accurately correcting gray curves for quadruple gamma values of y^1.0, y^1.8, y^2.2, and y^2.5. A test chip fabricated in a 6 V/0.7-μm triple-well CMOS process indicated that a gray voltage error was less than +8 mV, a gray-to-gray error-voltage difference was under +3 mV, and a pin-to-pin variation of each source driver output was +5 mV¹.