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Line inversion-based mobile TFT-LCD driver IC with novel quadruple-gamma-curve correction is presented. The driver IC allows for a cost-effective accurate curve correction for multiple gamma values of γ1.0, γ1.8, γ2.2, and γ2.5 by adopting novel voltage-symmetric gray curve synthesis and variable reference resistor-tap biasing schemes. A test chip in a 6 V/0.7-μm triple-well CMOS process indicated a gray voltage error of ±8 mV with gray-to-gray error difference under ±3 mV.

This paper analyzes and compares the penal power consumption for mobile TFT-LCDs. Three representative penal driving schemes (the basic data driving, the charge-recycling data driving, and the stepwise data driving) based on the line inversion driving method are considered in this analysis, and equations for representing the penal power consumption of respective driving schemes are derived. This is the first to analyze the panel power consumption of line inversion-based mobile TFT-LCDs including parasitic capacitance effect. The analysis procedure presented here is helpful for power study, and gives benefits of providing accurate estimation of the total power consumption of mobile TFT-LCDs driven a line inversion driving.

A circuit technique to detect unexpected power condition such as battery separation is presented. Abrupt power-off due to this unexpected power condition may cause an abnormal display in mobile TFT-LCD because adequate power-off sequence cannot be performed. To demonstrate feasibility of the APD, test chip was designed and fabricated in a 30-V/4-um 5-V/0.8-um 2.5-V/0.25-um triple-well CMOS process. Experimental results show that the proposed APD improves display quality by allowing a proper power-off sequence at all abrupt power-off conditions.

An opportunistic source line driving (OSLD) scheme is proposed for use in mobile TFT_LCD driver ICs (T-LDIs). In OSLD scheme, the operation of the source drivers of a T-LDI is controlled by the equivalence of RGB color data for adjacent pixels. That is, one source driver drives the neighboring source lines as well as the corresponding one when the color data of adjacent pixcels are identical to each other. With this scheme, all the source drivers associated with the neighboring source lines can be completely turned off, allowing the reduction of static and dynamic current of these drivers. Test chip was fabricated in a 5-V/0.8-um 2.5V/0.25-um triple-metal CMOS process, and the experimental result shows that the power reduction of 12% ~ 21% was obtained with die size overhead less than 0.5%.